zephyr: Fix uart_console_read_buffer_init() return value
zephyr: Fix uart_console_read_buffer_init() return value

This function should have a return value. Add it to avoid a warning.

BUG=b:180409973
BRANCH=none
TEST=warning is gone

Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Change-Id: I70562e3f4ddea1283099f93939abd3faef0476e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2705444
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>

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