bnxt_en: Fix TX push operation on ARM64.

There is a code path where we are calling __iowrite64_copy() on
an address that is not 64-bit aligned.  This causes an exception on
some architectures such as arm64.  Fix that code path by using
__iowrite32_copy().

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