make tlbflush_filter()'s first parameter a pointer

make tlbflush_filter()'s first parameter a pointer

This brings it in line with most other functions dealing with CPU
masks. Convert both implementations to inline functions at once.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com>