[PATCH, AArch64] Support --mcmodel=tiny.

[Marcus Shawcroft]

Hi, This patch adds support for the tiny absolute memory model.
Regressed for aarch64-none-elf with each of
  -mcmodel=tiny
  -mcmodel=small
  -mcmodel=small -fPIC

Applied.

/Marcus

2012-05-29  Chris Schlumberger-Socha <chris.schlumberger-so...@arm.com>
            Marcus Shawcroft  <marcus.shawcr...@arm.com>

        * config/aarch64/aarch64-protos.h (aarch64_symbol_type): Define
        SYMBOL_TINY_ABSOLUTE.
        * config/aarch64/aarch64.c (aarch64_load_symref_appropriately): 
Handle
        SYMBOL_TINY_ABSOLUTE.
        (aarch64_expand_mov_immediate): Likewise.
        (aarch64_classify_symbol): Likewise.
        (aarch64_mov_operand_p): Remove ATTRIBUTE_UNUSED.
        Permit SYMBOL_TINY_ABSOLUTE.
        * config/aarch64/predicates.md (aarch64_mov_operand): Permit CONST.