Merge changes from topic "xlat" into integration

* changes:
  xlat_tables_v2: fix assembler warning of PLAT_RO_XLAT_TABLES
  linker_script: move bss section to bl_common.ld.h
  linker_script: replace common read-only data with RODATA_COMMON
  linker_script: move more common code to bl_common.ld.h