hpfs: Remove unessary cast

Avoid a pointless kmem_cache_alloc() return value cast in
fs/hpfs/super.c::hpfs_alloc_inode()

Signed-off-by: Firo Yang <firogm@gmail.com>
Signed-off-by: Mikulas Patocka <mikulas@twibright.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>