i2c: mux: Fix error path in i2c-arb-gpio

There is no reason to use goto and just call return. Better is to call
return directly which is done for some if/else parts.

Also make no sense to setup ret to -ETIMEDOUT and then to 0.
Return timeout directly.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Heiko Schocher <hs@denx.de>