[libc] Enable exp10m1f on RISC-V (#138768)

Previously, the test failed due to isnan() and isinf() not being
defined.

This patch follows other tests in the same directory and calls isnan and
isinf from the FBits class.

---------

Co-authored-by: OverMighty <[email protected]>

Author: mikhailramalho

libc/config/linux/riscv/entrypoints.txt

@@ -451,7 +451,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.exp
     libc.src.math.exp10
     libc.src.math.exp10f
-    # libc.src.math.exp10m1f
+    libc.src.math.exp10m1f
     libc.src.math.exp2
     libc.src.math.exp2f
     libc.src.math.exp2m1f

libc/test/src/math/exp10m1f_test.cpp

@@ -80,7 +80,7 @@ TEST_F(LlvmLibcExp10m1fTest, InFloatRange) {
   constexpr uint32_t STEP = UINT32_MAX / COUNT;
   for (uint32_t i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
     float x = FPBits(v).get_val();
-    if (isnan(x) || isinf(x))
+    if (FPBits(v).is_inf_or_nan())
       continue;
     LIBC_NAMESPACE::libc_errno = 0;
     float result = LIBC_NAMESPACE::exp10m1f(x);
@@ -89,7 +89,7 @@ TEST_F(LlvmLibcExp10m1fTest, InFloatRange) {
     // in the single-precision floating point range, then ignore comparing with
     // MPFR result as MPFR can still produce valid results because of its
     // wider precision.
-    if (isnan(result) || isinf(result) || LIBC_NAMESPACE::libc_errno != 0)
+    if (FPBits(result).is_inf_or_nan() || LIBC_NAMESPACE::libc_errno != 0)
       continue;
     ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp10m1, x,
                                    LIBC_NAMESPACE::exp10m1f(x), 0.5);