AArch64: Fix assertions in processing dynamic relocations

AArch64: Fix assertions in processing dynamic relocations

This patch provides the following changes in fixup_gdt_reloc()
function:
- Fixes assertions in processing dynamic relocations, when
relocation entries not matching R_AARCH64_RELATIVE type are found.
Linker might generate entries of relocation type R_AARCH64_NONE
(code 0), which should be ignored to make the code boot. Similar
issue was fixed in OP-TEE (see optee_os/ldelf/ta_elf_rel.c
commit 7a4dc765c133125428136a496a7644c6fec9b3c2)
- Fixes bug when "b.ge" (signed greater than or equal) condition
codes were used instead of "b.hs" (greater than or equal) for
comparison of absolute addresses.
- Adds optimisation which skips fixing Global Object Table (GOT)
entries when offset value is 0.

Change-Id: I35e34e055b7476843903859be947b883a1feb1b5
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>