net: stmmac: use interrupt mode INTM=1 for multi-MSI

For interrupt mode INTM=0, TX/RX transfer complete will trigger signal
not only on sbd_perch_[tx|rx]_intr_o (Transmit/Receive Per Channel) but
also on the sbd_intr_o (Common).

As for multi-MSI implementation, setting interrupt mode INTM=1 is more
efficient as each TX intr and RX intr (TI/RI) will be handled by TX/RX ISR
without the need of calling the common MAC ISR.

Updated the TX/RX NORMAL interrupts status checking process as the
NIS status bit is not asserted for any RI/TI events for INTM=1.

Signed-off-by: Wong, Vee Khee <vee.khee.wong@intel.com>
Co-developed-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>