wil6210: add module parameter for alternate interface name

Add a module parameter alt_ifname that when set, will name
the primary network interface wigig<N> instead of the default
wlan<N>. This helps platforms such as android where we need to
clearly separate the WIGIG interface from the default wireless
interface.

Change-Id: Icd7e949da5401c877b3d1d674167b0fdcb133d18
CRs-Fixed: 982931
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>