delete include/vendor.sh and merge elsewhere

move it all to other files where items are used, and not
used anywhere else. this reduces the size of vendor.sh.

also remove a few redundant variables, or variables that
are not meaningfully used.

a few items have been moved to include/option.sh

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/mrc.sh

@@ -4,6 +4,8 @@
 # Modifications in this version are Copyright 2021 and 2023 Leah Rowe.
 # Original copyright detailed in repo: https://review.coreboot.org/coreboot/
 
+eval "$(setvars "" MRC_url MRC_url_bkup MRC_hash MRC_board)"
+
 extract_mrc()
 {
 	[ -z "${MRC_board}" ] && err "extract_mrc $MRC_hash: MRC_board not set"