[RISCV][compiler-rt] drop __riscv_vendor_feature_bits (llvm#126460)

Address riscv-non-isa/riscv-c-api-doc#101

(cherry picked from commit 2cd8207)

Author: BeMg

compiler-rt/lib/builtins/cpu_model/riscv.c

@@ -14,12 +14,6 @@ struct {
   unsigned long long features[RISCV_FEATURE_BITS_LENGTH];
 } __riscv_feature_bits __attribute__((visibility("hidden"), nocommon));
 
-#define RISCV_VENDOR_FEATURE_BITS_LENGTH 1
-struct {
-  unsigned length;
-  unsigned long long features[RISCV_VENDOR_FEATURE_BITS_LENGTH];
-} __riscv_vendor_feature_bits __attribute__((visibility("hidden"), nocommon));
-
 struct {
   unsigned mvendorid;
   unsigned long long marchid;
@@ -338,11 +332,11 @@ static int FeaturesBitCached = 0;
 void __init_riscv_feature_bits(void *);
 static void __init_riscv_feature_bits_ctor(void) CONSTRUCTOR_ATTRIBUTE;
 
-// A constructor function that sets __riscv_feature_bits, and
-// __riscv_vendor_feature_bits to the right values.  This needs to run
-// only once.  This constructor is given the highest priority and it should
-// run before constructors without the priority set.  However, it still runs
-// after ifunc initializers and needs to be called explicitly there.
+// A constructor function that sets __riscv_feature_bits
+// to the right values.  This needs to run only once.  This constructor is given
+// the highest priority and it should run before constructors without the
+// priority set.  However, it still runs after ifunc initializers and needs to
+// be called explicitly there.
 
 static void CONSTRUCTOR_ATTRIBUTE __init_riscv_feature_bits_ctor(void) {
   __init_riscv_feature_bits(0);
@@ -357,7 +351,6 @@ void __init_riscv_feature_bits(void *PlatformArgs) {
     return;
 
   __riscv_feature_bits.length = RISCV_FEATURE_BITS_LENGTH;
-  __riscv_vendor_feature_bits.length = RISCV_VENDOR_FEATURE_BITS_LENGTH;
 
 #if defined(__linux__)
   struct riscv_hwprobe Hwprobes[] = {