VHE: Remove branch protection in secure_aem_v8a_fvp_vhe builds

If hafnium is built with branch protection enabled, the current mmu code
ensures that branch protection is enforced on all stage 1 translation
tables. This includes S-EL0 partitions that run on VHE. Removing branch
protection in the VHE builds means that we dont have to force all S-EL0
partitions to be built with VHE enabled. This will be done at a later
time.

Signed-off-by: Raghu Krishnamurthy <raghu.ncstate@gmail.com>
Change-Id: I3871fb75a676e41d9bddddf26ebeb3c7d10e241e
diff --git a/BUILD.gn b/BUILD.gn
index 2f6a477..b5186a0 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -108,7 +108,6 @@
   heap_pages = 60
   max_cpus = 8
   max_vms = 16
-  branch_protection = "standard"
   toolchain_args = {
     plat_ffa = "//src/arch/aarch64/plat/ffa:spmc"
     plat_psci = "//src/arch/aarch64/plat/psci:spmc"