rc: syscons: Add UEFI special case

Changing cursor, screenmap and setting blanktime doesn't work when booted
with vt(4) and UEFI so add a special case for those depending on machdep.bootmethods.
I have no way to test if this can work with vt(4) and bios boot so just in case
keep calling those for this.

Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38293