[demangler][RISCV] Fix for long double

Summary:
The size of long double in RISCV (both RV32 and RV64) is 16 bytes, thus
the mangled_size shouble be 32.

This patch will fix test case
"_ZN5test01hIfEEvRAcvjplstT_Le4001a000000000000000E_c"
in test_demangle.pass.cpp, which is expected to be invalid but demangler
returned "void test0::h<float>(char (&) [(unsigned int)((sizeof (float))
+ (0x0.000000004001ap-16382L))])" in RISCV environment without this patch.

Reviewed By: urnathan

Differential Revision: https://reviews.llvm.org/D126480

GitOrigin-RevId: 842e48bd65770f0368ee0d1ca7ee34dbd8f0ff03

src/demangle/ItaniumDemangle.h

diff --git a/src/demangle/ItaniumDemangle.h b/src/demangle/ItaniumDemangle.h
index beece93..e3f0c6d 100644
--- a/src/demangle/ItaniumDemangle.h
+++ b/src/demangle/ItaniumDemangle.h
@@ -5099,7 +5099,7 @@
 struct FloatData<long double>
 {
 #if defined(__mips__) && defined(__mips_n64) || defined(__aarch64__) || \
-    defined(__wasm__)
+    defined(__wasm__) || defined(__riscv)
     static const size_t mangled_size = 32;
 #elif defined(__arm__) || defined(__mips__) || defined(__hexagon__)
     static const size_t mangled_size = 16;