Added SPI4/SPI5/SPI6 support to the STM32v1 SPIv1 low level driver.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/branches/stable_2.6.x@6531 35acf78f-673a-0410-8e92-d51de3d6d3f4