Operand sizes used for simulation of MSP430 hardware multiply
operations are not aligned with the sizes used on the target, resulting
in the simulator storing signed operands with too much precision.

Additionally, simulation of unsigned multiplication is missing explicit
casts to prevent any implicit sign extension.

gcc.c-torture/execute/pr91450-1.c uses unsigned widening multiplication
of 32-bit operands -4 and 2, to a 64-bit result:
0xffff fffc * 0x2 = 0x1 ffff fff8

If -4 is stored in 64-bit precision, then the multiplication is
essentially signed and the result is -8 in 64-bit precision
(0xffff ffff ffff fffc), which is not correct.

Successfully regtested the GCC and G++ DejaGNU testsuites for msp430-elf in the
default configuration, and with -mhwmult=f5series.
This patch fixes 158 execution failures for -mhwmult=f5series.

Ok to apply?

Thanks,
Jozef