Move pa.h FUNCTION_ARG_SIZE to pa.c (PR83858)

Move pa.h FUNCTION_ARG_SIZE to pa.c (PR83858)

The port-local FUNCTION_ARG_SIZE:

  ((((MODE) != BLKmode \
     ? (HOST_WIDE_INT) GET_MODE_SIZE (MODE) \
     : int_size_in_bytes (TYPE)) + UNITS_PER_WORD - 1) / UNITS_PER_WORD)

is used by code in pa.c and by ASM_DECLARE_FUNCTION_NAME in som.h.
Treating GET_MODE_SIZE as a constant is OK for the former but not
the latter, which is used in target-independent code.  This caused
a build failure on hppa2.0w-hp-hpux11.11.

2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR target/83858
	* config/pa/pa.h (FUNCTION_ARG_SIZE): Delete.
	* config/pa/pa-protos.h (pa_function_arg_size): Declare.
	* config/pa/som.h (ASM_DECLARE_FUNCTION_NAME): Use
	pa_function_arg_size instead of FUNCTION_ARG_SIZE.
	* config/pa/pa.c (pa_function_arg_advance): Likewise.
	(pa_function_arg, pa_arg_partial_bytes): Likewise.
	(pa_function_arg_size): New function.

From-SVN: r256744