mm: mremap: fix sign for EFAULT error return value

mm: mremap: fix sign for EFAULT error return value

The mremap syscall is supposed to return a pointer to the new virtual
memory area on success, and a negative value of the error code in case of
failure.  Currently, EFAULT is returned when the VMA is not found, instead
of -EFAULT.  The users of this syscall will therefore believe the syscall
succeeded in case the VMA didn't exist, as it returns a pointer to address
0xe (0xe being the value of EFAULT).  Fix the sign of the error value.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 550a7d60bd5e ("mm, hugepages: add mremap() support for hugepage backed vma")
Signed-off-by: Niels Dossche <[email protected]>
Cc: Mina Almasry <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>