s390: Emit relocation for 32-bit immediate operand

s390: Emit relocation for 32-bit immediate operand

IBM Z instruction format RIL-a has a 32-bit immediate operand in
instruction bits 16 to 47.  Enable the assembler to emit a 32-bit
direct or PC-relative relocation when processing a fixup, similar
as it is already done for 16-bit immediate operands in bits 16-31.

This enables to assemble the following:

	lgfi	%r1,symbol	# R_390_32
	lgfi	%r1,symbol-.	# R_390_PC32

Furthermore it brings GNU assembler on par with LLVM assembler in
that regard.

gas/
	* config/tc-s390.c (md_apply_fix): Emit 32-bit direct or
	PC-relative relocation for 32-bit immediate operand in
	instruction bits 16-47.

gas/testsuite/
	* gas/s390/zarch-reloc.d: Add tests for relocation of RIL-a
	32-bit immediate operand.
	* gas/s390/zarch-reloc.s: Likewise.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>