net: am79c961a: avoid %? in inline assembly

The am79c961a.c driver fails to build with clang because of an
unusual inline assembly construct:

drivers/net/ethernet/amd/am79c961a.c:53:7: error: invalid % escape in inline assembly string
 "str%?h        %1, [%2]        @ NET_RAP\n\t"

The same change has been done a decade ago in arch/arm as of
6a39dd62 ("[ARM] 3759/2: Remove uses of %?"), but apparently
some drivers were missed.

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