fm10k: fix Rx function selection

fm10k: fix Rx function selection

Steps to reproduce the bug:
1. All Rx offloading is disabled and start the device, then
   Vector Rx is used.
2. Stop the device. Re-configure to enable hw_ip_checksum = 1,
   start the device again.
3. In this case, assume regular Rx should be used since Vector
   Rx doesn't support ip checksum offload. But actually Vector
   Rx is used and cause checksum won't be done by hardware.

The reason is after re-configuring, driver misses an "else" in
func fm10k_set_rx_function(). Then Rx func in last round are
used.

Fixes: 77a8ab47eb38 ("fm10k: select best Rx function")

Reported-by: Xiao Wang <xiao.w.wang@intel.com>
Signed-off-by: Chen Jing D(Mark) <jing.d.chen@intel.com>
Acked-by: Xiao Wang <xiao.w.wang@intel.com>