internal: Move parallel logic into internal_par implementation

The parallel internal programmer is its own implementation. Move
it and call into it from the top-level internal.c programmer
implementation.

Change-Id: Idabeceb59a36680f5fbb45d3ee4bd5dbf837373b
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/71834
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-by: Thomas Heijligen <src@posteo.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

meson.build

@@ -246,6 +246,7 @@ programmer = {
       'board_enable.c',
       'cbtable.c',
       'internal.c',
+      'internal_par.c',
       'it87spi.c',
       'sb600spi.c',
       'superio.c',
@@ -261,6 +262,7 @@ programmer = {
       'cbtable.c',
       'chipset_enable.c',
       'internal.c',
+      'internal_par.c',
       'processor_enable.c',
       'pcidev.c',
       'known_boards.c',