gallium/swr: fix issues preventing a 32-bit build

Not a currently tested configuration, but these couple of small changes
allow a 32-bit build.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94383
Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Brian Paul <brianp@vmware.com>
2 files changed