procfs: simplify the binfmt_misc mount check
procfs: simplify the binfmt_misc mount check

Replace the `mountinfo` exec with a file test of the register file
which we rely on later anyways.

Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

OpenRC/openrc,dwfreed/openrc,williamh/openrc,OpenRC/openrc,dwfreed/openrc,dwfreed/openrc,OpenRC/openrc,williamh/openrc,williamh/openrc