octeontx2-pf: Fix unintentional sign extension issue

octeontx2-pf: Fix unintentional sign extension issue

The shifting of the u16 result from ntohs(proto) by 16 bits to the
left will be promoted to a 32 bit signed int and then sign-extended
to a u64.  In the event that the top bit of the return from ntohs(proto)
is set then all then all the upper 32 bits of a 64 bit long end up as
also being set because of the sign-extension. Fix this by casting to
a u64 long before the shift.

Addresses-Coverity: ("Unintended sign extension")
Fixes: f0c2982aaf98 ("octeontx2-pf: Add support for SR-IOV management function")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20201118130520.460365-1-colin.king@canonical.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>