MAINTAINERS: Add myself as VFIO-platform reviewer

Based on discussion:
https://lore.kernel.org/kvm/20250806170314.3768750-3-alex.williamson@redhat.com/

I will start looking into adding support for modern HW and more
features to VFIO-platform.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20250820203102.2034333-1-smostafa@google.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Author: misaleh

MAINTAINERS

@@ -26493,6 +26493,7 @@ F:	drivers/vfio/pci/pds/
 
 VFIO PLATFORM DRIVER
 M:	Eric Auger <eric.auger@redhat.com>
+R:	Mostafa Saleh <smostafa@google.com>
 L:	kvm@vger.kernel.org
 S:	Maintained
 F:	drivers/vfio/platform/