net: qfec: Fix error in GMAC_N_CLKDIV_SHFT macro

Fix incorrect bit shift in GMAC_N_CLKDIV_SHFT macro to set up the
correct clock divider for 100Mbps and 10Mbps operation.

Change-Id: I53bff914402a1f4960149f00ca61dc3d814a1996
Acked-by: Jie Luo <jluo@qti.qualcomm.com>
Signed-off-by: Venkatesh Yadav Abbarapu <quicvenkat@codeaurora.org>