defconfig: arm64: Enable CC_STACKPROTECTOR_STRONG for sdm855

Enable config flag CONFIG_CC_STACKPROTECTOR_STRONG on sdm855
for enabling -fstack-protector-strong compiler option.

Change-Id: I9ad41df97cc4239cd38486ac3bc3deeff061e8cf
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>