s390/mm,fault: remove VM_FAULT_BADCONTEXT

Remove VM_FAULT_BADCONTEXT and instead call do_no_context() via
wrappers. This adds two new wrappers similar to what x86 has:

handle_fault_error() and handle_fault_error_nolock(). Both of them
simply call do_no_context(), while handle_fault_error() also unlocks
mmap lock, which avoids adding lots of mmap_read_unlock() calls with
this and subsequent patches.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>