outmacho.mac: fix typo in subsections_via_symbols
outmacho.mac: fix typo in subsections_via_symbols

subsections_via_symbols is plural for both nouns.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm