linux-user: add comments for TARGET_NR_[gs]etgroups{,32}

There are 2 pairs of identical code (with different types)
for TARGET_NR_setgroups & TARGET_NR_setgroups32, and
for TARGET_NR_getgroups & TARGET_NR_getgroups32.  Add
comments stating this fact, so that further modifications
are done in two places.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
1 file changed