After the recent change in GAS [1], macro arguments must be quoted or
grouped with parenthesis. Add the necessary parenthesis in order to fix
assembly errors like:
mul.s:31: Error: too many positional arguments
[1] https://sourceware.org/pipermail/binutils/2024-July/136053.html
Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>