linker_script: move .rela.dyn section to bl_common.ld.h

linker_script: move .rela.dyn section to bl_common.ld.h

The .rela.dyn section is the same for BL2-AT-EL3, BL31, TSP.

Move it to the common header file.

I slightly changed the definition so that we can do "RELA_SECTION >RAM".
It still produced equivalent elf images.

Please note I got rid of '.' from the VMA field. Otherwise, if the end
of previous .data section is not 8-byte aligned, it fails to link.

aarch64-linux-gnu-ld.bfd: warning: changing start of section .rela.dyn by 4 bytes
aarch64-linux-gnu-ld.bfd: warning: changing start of section .rela.dyn by 4 bytes
aarch64-linux-gnu-ld.bfd: warning: changing start of section .rela.dyn by 4 bytes
make: *** [Makefile:1071: build/qemu/release/bl31/bl31.elf] Error 1

Change-Id: Iba7422d99c0374d4d9e97e6fd47bae129dba5cc9
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>