core: thread_a64.S: fix gcc 4.9 compile error
core: thread_a64.S: fix gcc 4.9 compile error

Fixes compile errors
out/arm-plat-hikey/core/arch/arm/kernel/thread_a64.o: In function `el0_sync_abort':
/home/bla/optee_os/core/arch/arm/kernel/thread_a64.S:778:(.text.el0_sync_abort+0xf4): relocation truncated to fit: R_AARCH64_TSTBR14 against `.text.thread_vect_table'
out/arm-plat-hikey/core/arch/arm/kernel/thread_a64.o: In function `elx_fiq':
/home/bla/optee_os/core/arch/arm/kernel/thread_a64.S:949:(.text.elx_fiq+0x9c): relocation truncated to fit: R_AARCH64_TSTBR14 against `.text.thread_vect_table'
make: *** [out/arm-plat-hikey/core/tee.elf] Error 1
experienced with some gcc 4.9 compiler

Fixes: https://github.com/OP-TEE/optee_os/issues/2067
Reviewed-by: Etienne Carriere <f21bc5b8f3ea1962eb45af359f1abea6578cab94@linaro.org>
Tested-by: Victor Chong <4aabb03bd6dd29c44a49684d87b08ac07e10b492@linaro.org> (hikey)
Signed-off-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os