drivers: spi_dw: Handle multiple interrupt lines for errors

This patch handles multiple interrupt lines for errors. Each of the
4 DW SPI error interrupts (txo_err, rxo_err, rxu_err, mst_err) can
use a different line of the GIC, instead of using a single line of
the GIC for all error interrupts (err_int).

Signed-off-by: Julien Panis <jpanis@baylibre.com>