Add flash_link_ro command to openocd
Add flash_link_ro command to openocd

This is ~4x as fast as flashing the entire EC image, and is similar to
the existing flash_link_a command.

BUG=none
TEST=from openocd prompt, flash_link_ro

Change-Id: I04160af3d7d70028f8d2789480094c283a1ce2ab
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26268
Reviewed-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>

eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,gelraen/cros-ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,longsleep/ec,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,md5555/ec,thehobn/ec,md5555/ec,md5555/ec,md5555/ec,fourier49/BIZ_EC,fourier49/BIZ_EC,fourier49/BIZ_EC,longsleep/ec,thehobn/ec,gelraen/cros-ec,longsleep/ec,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,alterapraxisptyltd/chromium-ec,gelraen/cros-ec,eatbyte/chromium-ec,coreboot/chrome-ec,eatbyte/chromium-ec,mtk09422/chromiumos-platform-ec,alterapraxisptyltd/chromium-ec,thehobn/ec,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,eatbyte/chromium-ec,gelraen/cros-ec,thehobn/ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,fourier49/BZ_DEV_EC