drm/amd/include/aldebaran_ip_offset: Mark top-level IP_BASE as __maybe_unused

drm/amd/include/aldebaran_ip_offset: Mark top-level IP_BASE as __maybe_unused

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:259:29: warning: ‘XGMI2_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:252:29: warning: ‘XGMI1_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:245:29: warning: ‘XGMI0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:238:29: warning: ‘WAFL1_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:231:29: warning: ‘WAFL0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:161:29: warning: ‘PCIE0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:119:29: warning: ‘L2IMU0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:112:29: warning: ‘L1IMUPCIE0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:105:29: warning: ‘L1IMUIOAGR0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:98:29: warning: ‘IOHC0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:91:29: warning: ‘IOAPIC0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:84:29: warning: ‘IOAGR0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:63:29: warning: ‘FUSE_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:49:29: warning: ‘DBGU_IO0_BASE’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/../include/aldebaran_ip_offset.h:42:29: warning: ‘CLK_BASE’ defined but not used [-Wunused-const-variable=]

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>