x86: Fix error return sequence in __ioremap_caller()

kernel missed to free memtype if get_vm_area_caller failed in
__ioremap_caller.

This patch introduces error path to fix this and cleans up the
repetitive error return sequences that contributed to the
creation of the bug.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <1257389031-20429-1-git-send-email-dfeng@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>