Loading 64bit constants require up to 4 load immediates, since
we can only load 16 bits at a time.  If the 32bit halves of
the 64bit constant are the same, however, we can save a cycle
by doing a register move instead of two loads of 16 bits.

Note that we don't optimize the normal ALU64 load because even
though it's a 64 bit load the upper half of the register is
a coming from sign extension so we can load it in one cycle
anyway.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>