rustc_target: Sync with stdarch (important parts)

Of RISC-V features defined in stdarch, this commit adds extensions
satisfying following criteria:

*   Formerly a part of the "I" extension and splitted thereafter
    (now ratified as "I" + "Zifencei" + "Zicsr" + "Zicntr" + "Zihpm") or
*   Dicoverable from newer versions of the Linux kernel ("Ztso").

This is based on the latest ratified ISA Manuals (version 20240411).

One of those, "Zicsr", is a dependency of many other ISA extensions and
this commit adds correct dependencies to "Zicsr" except "V"
(due to an ongoing PR).

Author: a4lg

compiler/rustc_target/src/target_features.rs

@@ -488,7 +488,7 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("c", Stable, &[]),
     ("d", Unstable(sym::riscv_target_feature), &["f"]),
     ("e", Unstable(sym::riscv_target_feature), &[]),
-    ("f", Unstable(sym::riscv_target_feature), &[]),
+    ("f", Unstable(sym::riscv_target_feature), &["zicsr"]),
     (
         "forced-atomics",
         Stability::Forbidden { reason: "unsound because it changes the ABI of atomic operations" },
@@ -516,19 +516,25 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("zdinx", Unstable(sym::riscv_target_feature), &["zfinx"]),
     ("zfh", Unstable(sym::riscv_target_feature), &["zfhmin"]),
     ("zfhmin", Unstable(sym::riscv_target_feature), &["f"]),
-    ("zfinx", Unstable(sym::riscv_target_feature), &[]),
+    ("zfinx", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zhinx", Unstable(sym::riscv_target_feature), &["zhinxmin"]),
     ("zhinxmin", Unstable(sym::riscv_target_feature), &["zfinx"]),
+    ("zicntr", Unstable(sym::riscv_target_feature), &["zicsr"]),
+    ("zicsr", Unstable(sym::riscv_target_feature), &[]),
+    ("zifencei", Unstable(sym::riscv_target_feature), &[]),
+    ("zihintpause", Unstable(sym::riscv_target_feature), &[]),
+    ("zihpm", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zk", Stable, &["zkn", "zkr", "zkt"]),
     ("zkn", Stable, &["zbkb", "zbkc", "zbkx", "zkne", "zknd", "zknh"]),
     ("zknd", Stable, &[]),
     ("zkne", Stable, &[]),
     ("zknh", Stable, &[]),
-    ("zkr", Stable, &[]),
+    ("zkr", Stable, &["zicsr"]),
     ("zks", Stable, &["zbkb", "zbkc", "zbkx", "zksed", "zksh"]),
     ("zksed", Stable, &[]),
     ("zksh", Stable, &[]),
     ("zkt", Stable, &[]),
+    ("ztso", Unstable(sym::riscv_target_feature), &[]),
     // tidy-alphabetical-end
 ];