w90p910_ether: remove incorrect __init annotation

The get_mac_address() function is normally inline, but when it is
not, we get a warning that this configuration is broken:

WARNING: vmlinux.o(.text+0x4aff00): Section mismatch in reference from the function w90p910_ether_setup() to the function .init.text:get_mac_address()
The function w90p910_ether_setup() references
the function __init get_mac_address().
This is often because w90p910_ether_setup lacks a __init

Remove the __init to make it always do the right thing.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>