fix compiler warnings in acorn.c

warning: 'adfs_partition' defined but not used
warning: 'riscix_partition' defined but not used
warning: 'linux_partition' defined but not used

Signed-off-by: Denver Gingerich <denver@ossguy.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>