Avoid unnecessary cast and bit shift

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Replace global net_device with link in spi_device

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Move interrupt counter to struct qcaspi

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>