UBUNTU: SAUCE: arm64: errata: Add -mpc-relative-literal-loads to erratum #843419 build flags

GCC6 (and Linaro's 2015.12 snapshot of GCC5) has a new default that uses
adrp/ldr or adrp/add to address literal pools. When CONFIG_ARM64_ERRATUM_843419
is enabled, modules built with this toolchain fail to load:

  [ 2.156817] module libahci: unsupported RELA relocation: 275

Longterm, this will likely be superseded by -mfix-cortex-a53-843419, which
should disable this optimization in the future.

Cc: stable at vger.kernel.org
Fixes: df057cc7 ("arm64: errata: add module build workaround for erratum #843419")
BugLink: http://bugs.launchpad.net/bugs/1533009
Suggested-by: Christophe Lyon <christophe.lyon at linaro.org>
Signed-off-by: dann frazier <dann.frazier at canonical.com>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

arch/arm64/Makefile

@@ -43,6 +43,7 @@ CHECKFLAGS	+= -D__aarch64__
 
 ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
 KBUILD_CFLAGS_MODULE	+= -mcmodel=large
+KBUILD_CFLAGS_MODULE	+= $(call cc-option, -mpc-relative-literal-loads)
 endif
 
 # Default value