sparc32 do_unassigned_access overhaul v2

sparc32 do_unassigned_access overhaul v2

According to pages 9-31 - 9-34 of "SuperSPARC & MultiCache Controller
User's Manual":

1. "A lower priority fault may not overwrite the
    MFSR status of a higher priority fault."
2. The MFAR is overwritten according to the policy defined for the MFSR
3. The overwrite bit is asserted if the fault status register (MFSR)
   has been written more than once by faults of the same class
4. SuperSPARC will never place instruction fault addresses in the MFAR.

Implementation of points 1-3 allows booting Solaris 2.6 and 2.5.1.

v2: CODING_STYLE fixes

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>