bnxt_en: Add cache line size setting to optimize performance.

The chip supports 64-byte and 128-byte cache line size for more optimal
DMA performance when matched to the CPU cache line size.  The default is 64.
If the system is using 128-byte cache line size, set it to 128.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>