ec: add mtlrvpp_npcx to flash_ec script
ec: add mtlrvpp_npcx to flash_ec script

Enable flashing of mtlrvpp_npcx from flash_ec script

BUG=b:229073490
BRANCH=none
TEST=verify flashing of ec image works on mtlrvpp_npcx

Signed-off-by: Brandon Breitenstein <aebec3ef02c51d3d720a4de157ebeaefa44de382@intel.com>
Change-Id: I8a85c53eacbc7b89a5347b06a54aa197e1269600
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3585290
Reviewed-by: Vijay P Hiremath <006c712879a3af08bfdb5c2b8491a8b2d5fd73cd@intel.com>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec