target/arm: Implement FEAT_HBC

FEAT_HBC (Hinted conditional branches) provides a new instruction
BC.cond, which behaves exactly like the existing B.cond except
that it provides a hint to the branch predictor about the
likely behaviour of the branch.

Since QEMU does not implement branch prediction, we can treat
this identically to B.cond.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -815,6 +815,7 @@ uint32_t get_elf_hwcap2(void)
     GET_FEATURE_ID(aa64_sme_f64f64, ARM_HWCAP2_A64_SME_F64F64);
     GET_FEATURE_ID(aa64_sme_i16i64, ARM_HWCAP2_A64_SME_I16I64);
     GET_FEATURE_ID(aa64_sme_fa64, ARM_HWCAP2_A64_SME_FA64);
+    GET_FEATURE_ID(aa64_hbc, ARM_HWCAP2_A64_HBC);
 
     return hwcaps;
 }