MSP430: Fix inconsistent naming of hwmult libfuncs

MSP430: Fix inconsistent naming of hwmult libfuncs

The naming scheme used by GCC to reference MSP430 hardware multiply
library functions is inconsistent.

Sometimes the "GCC" names (e.g. mulsi2) are used, other times the
"MSPABI" names (e.g. __mspabi_mpyl) are used.

Also, sometimes an identifier for the hardware multiply support is
appended to the GCC name, when the functions are defined, but this is
not required.

This patch fixes those issues, so the names used to refer to the
hardware multiply library functions follow a consistent pattern.

gcc/ChangeLog:

	* config/msp430/msp430.c (msp430_output_labelref): Don't process mspabi
	hwmult library function names into GCC-style names.

libgcc/ChangeLog:

	* config/msp430/lib2hw_mul.S: Omit _hw* suffix from GCC names for
	hwmult library functions.

gcc/testsuite/ChangeLog:

	* gcc.target/msp430/rtx-cost-Os-f5series.c: Adjust test to use new
	hwmult library function name.