Change the size field of MSP430_Opcode_Decoded to a plain integer.

Change the size field of MSP430_Opcode_Decoded to a plain integer.

The size field was defined as an instance of an enum, but existing code
treats the size field as a plain integer containing a bit count.

include/ChangeLog:

	* opcode/msp430-decode.h (MSP430_Size): Remove.
	(Msp430_Opcode_Decoded): Change type of size to int.