sys/x86/NOTES: Add vt_efifb
Contrary to what is stated in commit f224591746bd ("Add ASMC_DEBUG make
option"), the various NOTES files should list all available options.
Since vt_efifb is supported also on i386, add it back to x86/NOTES
instead of amd64/NOTES.
Fixes: f224591746bd ("Add ASMC_DEBUG make option")
Sponsored by: The FreeBSD Foundation