LoongArch: Define the macro ASM_PREFERRED_EH_DATA_FORMAT by checking the assembler...

LoongArch: Define the macro ASM_PREFERRED_EH_DATA_FORMAT by checking the assembler's support for eh_frame encoding.

.eh_frame DW_EH_PE_pcrel encoding format is not supported by gas <= 2.39.
Check if the assembler support DW_EH_PE_PCREL encoding and define .eh_frame
encoding type.

gcc/ChangeLog:

	* config.in: Regenerate.
	* config/loongarch/loongarch.h (ASM_PREFERRED_EH_DATA_FORMAT):
	Select the value of the macro definition according to whether
	HAVE_AS_EH_FRAME_PCREL_ENCODING_SUPPORT is defined.
	* configure: Regenerate.
	* configure.ac: Reinstate HAVE_AS_EH_FRAME_PCREL_ENCODING_SUPPORT test.