sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
(mm: retry page fault when blocking on disk transfer) and
commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
(x86,mm: make pagefault killable)

The above commits introduced changes into the x86 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Port these changes to 64-bit sparc.

Signed-off-by: Kautuk Consul <[email protected]>
Signed-off-by: David S. Miller <[email protected]>