drm/amd/display: Don't build DCN1 when kcov is enabled

drm/amd/display: Don't build DCN1 when kcov is enabled

DCN1 contains code that utilizes fp math. When
CONFIG_KCOV_INSTRUMENT_ALL and CONFIG_KCOV_ENABLE_COMPARISONS are
enabled, build errors are found. See this earlier patch for details:

https://lists.freedesktop.org/archives/dri-devel/2018-August/186131.html

As a short term solution, disable CONFIG_DRM_AMD_DC_DCN1_0 when
KCOV_INSTRUMENT_ALL and KCOV_ENABLE_COMPARISONS are enabled. In
addition, make it a fully derived config, taking into account
CONFIG_X86.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>