cortex-m: Fix sysjump to RO with CONFIG_RO_HEAD_ROOM
cortex-m: Fix sysjump to RO with CONFIG_RO_HEAD_ROOM

This accounts for the extra head room in the RO image.

BRANCH=none
BUG=chrome-os-partner:43025, chrome-os-partner:44625
TEST=the cr50 image validates *and jumps to* the RW image at boot.

Change-Id: I8c87e7a9e7da187c19f135176ae5144cbc609cb9
Signed-off-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/296453
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>

akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec