Although 27.9mbps is possible at 100 MHz clock, switching down to 22mbps for microblaze 66.67 MHz clock

Adding more SPI master test scripts, including loopback, which verifies the non-XPS implementation works at up to 28mbps

Adding more SPI master test scripts, including loopback, which verifies the non-XPS implementation works at up to 28mbps

Signed-off-by: Mike Lyons <github@explosivedonut.com>