mips: spi: mscc: Add fast bitbang SPI driver

This patch add a new SPI driver for MSCC SOCs that does not sport the
designware SPI hardware controller.

Performance gain: 7.664 seconds vs. 17.633 for 1 Mbyte write.

Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 392a925..4acec3e 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -36,6 +36,7 @@
 obj-$(CONFIG_MPC8XXX_SPI) += mpc8xxx_spi.o
 obj-$(CONFIG_MTK_QSPI) += mtk_qspi.o
 obj-$(CONFIG_MT7621_SPI) += mt7621_spi.o
+obj-$(CONFIG_MSCC_BB_SPI) += mscc_bb_spi.o
 obj-$(CONFIG_MVEBU_A3700_SPI) += mvebu_a3700_spi.o
 obj-$(CONFIG_MXC_SPI) += mxc_spi.o
 obj-$(CONFIG_MXS_SPI) += mxs_spi.o