NET: am79c961: fix assembler warnings

Fix:
/tmp/ccvoZ6h8.s: Assembler messages:
/tmp/ccvoZ6h8.s:284: Warning: register range not in ascending order
/tmp/ccvoZ6h8.s:881: Warning: register range not in ascending order
/tmp/ccvoZ6h8.s:1087: Warning: register range not in ascending order

by ensuring that we have temporary variables placed into specific
registers.  Reorder the code a bit to allow the resulting assembly
to be slightly more optimal.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>