mm: introduce vmf_insert_pfn_prot()

Like vm_insert_pfn_prot(), but returns a vm_fault_t instead of an errno.
Also unexport vm_insert_pfn_prot as it has no modular users.

Link: http://lkml.kernel.org/r/20180828145728.11873-4-willy@infradead.org


Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>