fix target.cfg files on dell latitudes

some latitudes still used the old style for variables
in target.cfg, specifically arch="x86_64" - lbmk used to
then check that on a big if/else and translate it to the
correct target name for crossgcc, e.g. i386-elf, arm-eabi

now it just puts the arch directly, in a new variable:
xarch

change arch="x86_64" to xarch="i386-elf" in these files.
also remove a few obsolete variables. should build now.

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

config/coreboot/e5420_6mb/target.cfg

@@ -1,6 +1,5 @@
 tree="default"
-romtype="normal"
-arch="x86_64"
+xarch="i386-elf"
 payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="y"
@@ -8,5 +7,4 @@ payload_memtest="y"
 payload_seabios_withgrub="y"
 payload_seabios_grubonly="y"
 grub_scan_disk="ahci"
-microcode_required="n"
 status="unstable"

config/coreboot/e5520_6mb/target.cfg

@@ -1,6 +1,5 @@
 tree="default"
-romtype="normal"
-arch="x86_64"
+xarch="i386-elf"
 payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="y"
@@ -8,5 +7,4 @@ payload_memtest="y"
 payload_seabios_withgrub="y"
 payload_seabios_grubonly="y"
 grub_scan_disk="ahci"
-microcode_required="n"
 status="unstable"

config/coreboot/e6420_10mb/target.cfg

@@ -1,6 +1,5 @@
 tree="default"
-romtype="normal"
-arch="x86_64"
+xarch="i386-elf"
 payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="y"
@@ -8,5 +7,4 @@ payload_memtest="y"
 payload_seabios_withgrub="y"
 payload_seabios_grubonly="y"
 grub_scan_disk="ahci"
-microcode_required="n"
 status="unstable"

config/coreboot/e6520_10mb/target.cfg

@@ -1,6 +1,5 @@
 tree="default"
-romtype="normal"
-arch="x86_64"
+xarch="i386-elf"
 payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="y"
@@ -8,5 +7,4 @@ payload_memtest="y"
 payload_seabios_withgrub="y"
 payload_seabios_grubonly="y"
 grub_scan_disk="ahci"
-microcode_required="n"
 status="unstable"