drm/amd/powerplay: use true, false for bool variable in smu7_hwmgr.c

Fixes coccicheck warning:

drivers/gpu/drm/amd/powerplay/hwmgr/smu7_hwmgr.c:723:2-50: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/powerplay/hwmgr/smu7_hwmgr.c:733:3-52: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/powerplay/hwmgr/smu7_hwmgr.c:747:3-51: WARNING: Assignment of 0/1 to bool variable

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>