x86/pkeys: Move read_pkru() and write_pkru()

x86/pkeys: Move read_pkru() and write_pkru()

write_pkru() was originally used just to write to the PKRU register.  It
was mercifully short and sweet and was not out of place in pgtable.h with
some other pkey-related code.

But, later work included a requirement to also modify the task XSAVE
buffer when updating the register.  This really is more related to the
XSAVE architecture than to paging.

Move the read/write_pkru() to asm/pkru.h.  pgtable.h won't miss them.

Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]