drivers: amdgpu: amdgpu_display: Fixed the spelling of falg to flag

s/falg/flag/p

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>