sparc32: unaligned memory access (MNA) trap handler bug

Since commit f0e98c38 ("[SPARC]: Fix
link errors with gcc-4.3") the MNA trap handler does not emulate
stores to unaligned addresses correctly. MNA operation from both
kernel and user space are affected.

A typical effect of this bug is nr_frags in skbs are overwritten
during buffer copying/checksum-calculation, or maximally 6 bytes
of data in the network buffer will be overwitten with garbage.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>