net: sparx5: fix bitmask on 32-bit targets

I saw the build failure that was fixed in commit 6387f65e ("net:
sparx5: fix compiletime_assert for GCC 4.9") and noticed another
issue that was introduced in the same patch: Using GENMASK() to
create a 64-bit mask does not work on 32-bit architectures.

This probably won't ever happen on this driver since it's specific
to a 64-bit SoC, but it's better to write it portably, so use
GENMASK_ULL() instead.

Fixes: f3cad261

 ("net: sparx5: add hostmode with phylink support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>