drm/ast: Disable fast reset after DRAM initial

drm/ast: Disable fast reset after DRAM initial

[Bug][AST2500]

V1:
When AST2500 acts as stand-alone VGA so that DRAM and DVO initialization
have to be achieved by VGA driver with P2A (PCI to AHB) enabling.
However, HW suggests disable Fast reset mode after DRAM initializaton,
because fast reset mode is mainly designed for ARM ICE debugger.
Once Fast reset is checked as enabling, WDT (Watch Dog Timer) should be
first enabled to avoid system deadlock before disable fast reset mode.

V2:
Use to_pci_dev() to get revision of PCI configuration.

V3:
If SCU00 is not unlocked, just enter its password again.
It is unnecessary to clear AHB lock condition and restore WDT default
setting again, before Fast-reset clearing.

V4:
repatch after "error : could not build fake ancestor" resolved.

V5:
Since CVE_2019_6260 item3, Most of AST2500 have disabled P2A(PCIe to AMBA).
However, for backward compatibility, some patches about P2A, such as items
of v5.2 and v5.3, are considered to be upstreamed with comments.
1. Add define macro to improve source readability.
ast_drv.h, ast_main.c, ast_post.c
2. Add comment about "Fast restet" is enabled for ARM-ICE debugger
ast_post.c
3. Add comment about Reset USB port to patch USB unknown device issue
ast_post.c

Signed-off-by: KuoHsiang Chou <kuohsiang_chou@aspeedtech.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210709080900.4056-1-kuohsiang_chou@aspeedtech.com