or1k: Support large plt_relocs when generating plt entries

The current PLT generation code will generate invalid code when the PLT
relocation offset exceeds 64k.  This fixes the issue by detecting large
plt_reloc offsets and generare code sequences to create larger plt
relocations.

The "large" plt code needs 2 extra instructions to create 32-bit offsets.

bfd/ChangeLog:

	PR 27746
	* elf32-or1k.c (PLT_ENTRY_SIZE_LARGE, PLT_MAX_INSN_COUNT,
	OR1K_ADD, OR1K_ORI): New macros to help with plt creation.
	(elf_or1k_link_hash_table): New field plt_count.
	(elf_or1k_link_hash_entry): New field plt_index.
	(elf_or1k_plt_entry_size): New function.
	(or1k_write_plt_entry): Update to support variable size PLTs.
	(or1k_elf_finish_dynamic_sections): Use new or1k_write_plt_entry
	API.
	(or1k_elf_finish_dynamic_symbol): Update to write large PLTs
	when needed.
	(allocate_dynrelocs): Use elf_or1k_plt_entry_size to account for
	PLT size.

ld/ChangeLog:

	PR 27746
	testsuite/ld-or1k/or1k.exp (or1kplttests): Add tests for linking
	along with gotha() relocations.
	testsuite/ld-or1k/gotha1.dd: New file.
	testsuite/ld-or1k/gotha1.s: New file.
	testsuite/ld-or1k/gotha2.dd: New file.
	testsuite/ld-or1k/gotha2.s: New file
	testsuite/ld-or1k/pltlib.s (x): Define size to avoid link
	failure.