vmrun.sh: Don't require firmware on amd64 unless -E was specified

Approved by: re (cperciva)
PR: 290232
Reported by: David Marker <dave@freedave.net>
Fixes: aa34b1d20e44 ("vmrun.sh: Add arm64 support")
MFC after: 3 days

(cherry picked from commit f19f17b3af675fbbc1244b66bbd8fb4a9836cb02)
(cherry picked from commit 6c5540eebcf25e3f81c3ec9bfa762390d2a86885)