generic: fix adm6996 init

Kernel 3.14 added aditional genphy_soft_reset phy reset to phy_init_hw in drivers/net/phy/phy_device.c
Since adm6996 does in driver soft reset and doesn't use BMCR_RESET for soft reset
add dummy soft_reset callback to adm6996 driver, like it is done in ar8216.

This fixes ticket #20147

Signed-off-by: Andrej Vlasic <andrej.vlasic0@gmail.com>

SVN-Revision: 47272