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/MAINTAINERS b/MAINTAINERS
index d474dfa..1039269 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -524,6 +524,7 @@
 F:	board/mscc/
 F:	configs/mscc*
 F:	drivers/gpio/mscc_sgpio.c
+F:	drivers/spi/mscc_bb_spi.c
 F:	include/configs/vcoreiii.h
 
 MIPS JZ4780