trembyle: change set_mux calls to be board names
trembyle: change set_mux calls to be board names

ps8802_set_mux and ps8818_set_mux were confusing
at the board level with the same names as the main
driver function names.  So added board_ in front

BUG=none
BRANCH=none
TEST=make buildall -j

Signed-off-by: Denis Brockus <6b21e8190fb5e373363fb95271367073a16474ef@chromium.org>
Change-Id: I2123b0d11823b5a01e14a8efb58cf579dc513d2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2095530
Reviewed-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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