winsys/amdgpu: avoid potential segfault in amdgpu_bo_map()
winsys/amdgpu: avoid potential segfault in amdgpu_bo_map()

cs can be NULL when it comes from r600_buffer_map_sync_with_rings()
to avoid doing the same checks. It was checked for write mappings
but not for read mappings.

Cc: "17.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <506e97eed81d9e59d22f4c73fb51123bb62b4a30@gmail.com>
Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler