ixgbe/base: fix X550em flow control to be KR only
ixgbe/base: fix X550em flow control to be KR only

The code in the if statement is specific to the KR PHY. However,
the conditional was only checking for backplane. If the driver
was using the KX4 backplane PHY, this code would execute but
would write to the wrong PHY.

Signed-off-by: Wenzhuo Lu <58cb9036bdff9a5412edc3b9f70e105ccf59954f@intel.com>
Acked-by: Helin Zhang <aba9dfdb1a6ec8bf1ff66b95272c029f8dfde1b1@intel.com>

mixja/dpdk,venkynv/dpdk-mirror,mixja/dpdk,tsphillips/dpdk-fork,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,mixja/dpdk,john-mcnamara-intel/dpdk,mixja/dpdk,venkynv/dpdk-mirror,tsphillips/dpdk-fork,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,msune/dpdk,msune/dpdk,msune/dpdk,tsphillips/dpdk-fork,msune/dpdk,venkynv/dpdk-mirror,tsphillips/dpdk-fork