drm/amdgpu: Remove redundant call to priority_is_valid()

Remove a redundant call to amdgpu_ctx_priority_is_valid() from
amdgpu_ctx_priority_permit(), which is called from amdgpu_ctx_init() which is
called from amdgpu_ctx_alloc() which is called from amdgpu_ctx_ioctl(), where
we've called amdgpu_ctx_priority_is_valid() already first thing in the
function.

Cc: Alex Deucher <Alexander.Deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20231018010359.30393-1-luben.tuikov@amd.com