msm: emac: Fix the problem in flow control config

Fix the issue that the flow control in MAC does not setup correctly.

Change-Id: Iacc3f261865d06e39710c356dc0dd868e101d889
Acked-by: Jie Luo <jluo@qti.qualcomm.com>
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>