solaris2.em: Fold after_allocation into before_allocation

solaris2.em: Fold after_allocation into before_allocation

Since all ELF linkers call check_relocs after opening all inputs, we
can fold after_allocation into before_allocation so that local dynamic
symbols will be placed before global dynamic symbols in .dynsym section.
This fixed:

FAIL: Common symbol override test (auxiliary shared object build)
FAIL: ld-elf/pr19617a
FAIL: ld-elf/pr19698

for i386-solaris2.12 and x86_64-solaris2.12 targets.

	PR ld/22728
	* emultempl/solaris2.em (elf_solaris2_after_allocation): Fold
	into ...
	(elf_solaris2_before_allocation): This.
	(LDEMUL_AFTER_ALLOCATION): Removed.