MIPS/GAS/testsuite: Run the div macro test across architectures

MIPS/GAS/testsuite: Run the div macro test across architectures

The division macros expand differently depending on the ISA selected, so
run the 'div' macro test across compatible architectures, adopting the
'div-ilocks' test orphaned by commit 23fce1e31156 ("MIPS16 intermix test
failure"), <https://sourceware.org/ml/binutils/2009-01/msg00335.html>,
and providing coverage for the expansion variants.

Only run from MIPS III up for now and remove the ISA override from the
source, so that the 64-bit instructions are covered for individual
64-bit architectures.