xbmk: tidy up some if statements

this is an extension of the previous work to unroll
most of the condensed code lines.

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

include/rom.sh

@@ -197,7 +197,6 @@ mkcorebootbin_real()
 	if [ -z "$grub_scan_disk" ]; then
 		grub_scan_disk="nvme ahci ata"
 	fi
-
 	if [ -z "$grubtree" ]; then
 		grubtree="default"
 	fi
@@ -408,7 +407,6 @@ cprom()
 	if [ -n "$displaymode" ]; then
 		newrom="${newrom%.rom}_$displaymode.rom"
 	fi
-
 	if [ $# -gt 0 ] && [ "${1%.gkb}" != "$1" ]; then
 		tmpnew="${1##*/}"
 		newrom="${newrom%.rom}_${tmpnew%.gkb}.rom"