x86/mm: Use pgprotval_t in protval_4k_2_large() and protval_large_2_4k()

Use the proper type for "raw" page table values.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200422170116.GA28345@lst.de