Fixed SPI driver init function not clearing SPI2X bit when not needed.

Fixed PREVENT ALLOW MEDIUM REMOVAL command issuing in the MassStorageHost demo using incorrect parameters (thanks to Mike Alex).

Fixed MassStorageHost demo broken due to an incorrect if statement test in MassStore_GetReturnedStatus().

LUFA/Drivers/Peripheral/SPI.h

@@ -102,7 +102,9 @@
 				          (PrescalerMask & ~SPI_USE_DOUBLESPEED));
 				
 				if (PrescalerMask & SPI_USE_DOUBLESPEED)
-				  SPSR = (1 << SPI2X);
+				  SPSR |= (1 << SPI2X);
+				else
+				  SPSR &= ~(1 << SPI2X);
 			}
 			
 			/** Sends and receives a byte through the SPI interface, blocking until the transfer is complete.