[KINETIS] K20x SPI use separate rx/tx dummy bytes.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@7310 35acf78f-673a-0410-8e92-d51de3d6d3f4
Added chMBResetI().

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@7313 35acf78f-673a-0410-8e92-d51de3d6d3f4
Renamed chMBSizeI() in chMBGetSizeI().

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@7314 35acf78f-673a-0410-8e92-d51de3d6d3f4
Merge remote-tracking branch 'upstream/master'