Staging/pohmelfs: fix write_inode parameter warning

sparse warns that:
drivers/staging/pohmelfs/inode.c:1797: warning: initialization from incompatible pointer type

so fix pohmelfs_write_inode() to have the expected parameters.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>