s390/mm: Simplify get_fault_type()

s390/mm: Simplify get_fault_type()

With the gmap code gone get_fault_type() can be simplified:

- every fault with user_mode(regs) == true must be a fault in user address
  space

- every fault with user_mode(regs) == false is only a fault in user
  address space if the used address space is the secondary address space

- every other fault is within the kernel address space

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Link: https://lore.kernel.org/r/20241022120601.167009-10-imbrenda@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>