tcpci: tcpci_tcpm_set_polarity should not clobber
tcpci: tcpci_tcpm_set_polarity should not clobber

Bits 1-7 were getting clobbered when we updated Bit 0

BUG=none
BRANCH=none
TEST=verify tcpci still functions

Change-Id: Ida60a08aa9e250e1dfb640caff44efc75c8ca1a9
Signed-off-by: Denis Brockus <6b21e8190fb5e373363fb95271367073a16474ef@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1956438
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