zephyr: riscv: Drop gp register from panic data
zephyr: riscv: Drop gp register from panic data

In v2.7, the gp register was removed from the data collected during a
fatal error.  See this PR for more details:
https://github.com/zephyrproject-rtos/zephyr/pull/36235

Since that PR implies gp has no useful value, let's just drop it from
the panic data.

BUG=b:198824039
BRANCH=none
TEST=build with Zephyr main branch for hayato
     note: still fails at link step due to missing symbol
     "_image_rom_size"

Change-Id: Ia917d50c193fd2e493612a6d2dd6c0c6d92a1e6b
Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3160405
Commit-Queue: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Commit-Queue: Denis Brockus <6b21e8190fb5e373363fb95271367073a16474ef@chromium.org>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Reviewed-by: Denis Brockus <6b21e8190fb5e373363fb95271367073a16474ef@chromium.org>

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