Merge pull request riscv-collab#1093 from en-sc/en-sc/v-ext-csrs

target/riscv: vector CSRs are optional

Author: en-sc

src/target/riscv/riscv_reg.c

@@ -397,6 +397,14 @@ static bool gdb_regno_exist(const struct target *target, uint32_t regno)
 		case CSR_FRM:
 		case CSR_FCSR:
 			return riscv_supports_extension(target, 'F');
+		case CSR_VSTART:
+		case CSR_VXSAT:
+		case CSR_VXRM:
+		case CSR_VL:
+		case CSR_VCSR:
+		case CSR_VTYPE:
+		case CSR_VLENB:
+			return vlenb_exists(target);
 		case CSR_SCOUNTEREN:
 		case CSR_SSTATUS:
 		case CSR_STVEC: