zephyr: shim: SHI: fix bug
zephyr: shim: SHI: fix bug

This is the follow-up CL to fix the bug addressed in the comment of the
CL:2786888

BUG=b:182600858
BRANCH=none
TEST=pass zmake build

Signed-off-by: Jun Lin <4865d89268068846db8afe2dcacc793288c792a0@nuvoton.com>
Change-Id: Id1923f3dc0ac357cbcac876a5e68f304024867ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2799336
Tested-by: CH Lin <49997681dc186e71092740314bf6c6feeca6e227@nuvoton.com>
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Commit-Queue: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

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