Refactor PRINT_FPHEX_LONG_DOUBLE into a reusable macro

Refactor PRINT_FPHEX_LONG_DOUBLE into a reusable macro

This patch refactors the macro PRINT_FPHEX_LONG_DOUBLE from the file
sysdeps/ieee754/ldbl-128/printf_fphex.c into a function-like macro to
enable its use for both long double and _Float128, when they are
ABI-distinct.

	* sysdeps/ieee754/ldbl-128/printf_fphex.c: Include
	ldbl-128/printf_fphex_macros.h for the definition of PRINT_FPHEX.
	(PRINT_FPHEX_LONG_DOUBLE): Define based on PRINT_FPHEX.
	* sysdeps/ieee754/ldbl-128/printf_fphex_macros.h
	(PRINT_FPHEX): New function-like macro that can be used for long
	double, as well as for _Float128