or1k: Avoid R_OR1K_GOT16 overflow failures in presence of R_OR1K_GOT_AHI16

Now that we support R_OR1K_GOT_AHI16 we can relax the R_OR1K_GOT16
overflow validation check if the section has R_OR1K_GOT_AHI16.

We cannot simple disable R_OR1K_GOT16 overflow validation as there will
still be binaries that will have only R_OR1K_GOT16.  The
R_OR1K_GOT_AHI16 relocation will only be added by GCC when building with
the option -mcmodel=large.

This assumes that R_OR1K_GOT_AHI16 will come before R_OR1K_GOT16, which
is the code pattern that will be emitted by GCC.

bfd/ChangeLog:

	PR 21464
	* elf32-or1k.c (or1k_elf_relocate_section): Relax R_OR1K_GOT16
	overflow check if we have R_OR1K_GOT_AHI16 followed by
	R_OR1K_GOT16.