volteer: change mutex for Zephyr
volteer: change mutex for Zephyr

Change mutex structure name so it can be used by both ECOS and Zephyr.

BUG=b:173507858
BRANCH=none
TEST=make buildall -j8
build volteer on zephyr

Signed-off-by: Hyungwoo Yang <396fb9bf4e83ae7ab277be1e3696c2d747b99874@intel.corp-partner.google.com>
Change-Id: I797bb3335cb481e1d471635e5c9f11d48f2d37f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2638911
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
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