arm: fix testsuite fallout on arm-elf and arm-nto from FPA removal

Removing FPA means that in some cases we default to 'no-fpu' in the
assembler when previously we would have picked FPA-format floating
numbers.  This patch fixes the testsuite fallout on a couple of
targets that are affected by this change.  Where possible we do this
by adding an option to set the floating-point format, but for bad-bss
we just skip the test.