sim: pru: Fix test case assembly with latest GAS

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>
1 file changed