[libc][nfc][obvious] fix typos in FPUtil

[michaelrj]

Summary

Fix minor typos in FPUtil comments.

libc/src/__support/FPUtil/FMA.h

 #elif defined(__aarch64__)
 #include "aarch64/FMA.h"
 #else
 #include "generic/FMA.h"
 
 namespace __llvm_libc {
 namespace fputil {
 
-// We have a generic implementation available only for single precision fma os
+// We have a generic implementation available only for single precision fma as
 // we restrict it to float values for now.
 template <typename T>
 static inline cpp::EnableIfType<cpp::IsSame<T, float>::Value, T> fma(T x, T y,
                                                                      T z) {
   return generic::fma(x, y, z);
 }
 
 } // namespace fputil
 } // namespace __llvm_libc
 
 #endif
 
 #endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_FMA_H

libc/src/__support/FPUtil/Sqrt.h

if (bits.isInfOrNaN()) {
     return x;
   } else if (bits.getSign()) {
     // sqrt( negative numbers ) = NaN
     return FPBits<T>::buildNaN(One >> 1);
   } else {
     int xExp = bits.getExponent();
     UIntType xMant = bits.getMantissa();
 
-    // Step 1a: Normalize denormal input and append hiddent bit to the mantissa
+    // Step 1a: Normalize denormal input and append hidden bit to the mantissa
     if (bits.getUnbiasedExponent() == 0) {
       ++xExp; // let xExp be the correct exponent of One bit.
       internal::normalize<T>(xExp, xMant);
     } else {
       xMant |= One;
     }
 
     // Step 1b: Make sure the exponent is even.

libc/src/__support/FPUtil/generic/README.md

 This directory contains machine independent implementations of floating point
 operations. The implementations are nested in the namespace
 `__llvm_libc::fputil::generic`. This is to facilitate calling these generic
 implementations from machine dependent implementations. Consider the example of
 the fuse-multiply-add operation (FMA). The C standard library requires three
 different flavors, `fma` which operates double precsion numbers, `fmaf` which
-operates on single precision numbers, and `fmal` which operates on `lond double`
+operates on single precision numbers, and `fmal` which operates on `long double`
 numbers. On Aarch64, there are hardware instructions which implement the single
 and double precision flavors but not the `long double` flavor. For such targets,
 we want to be able to call the generic `long double` implementation from the
 `long double` flavor. By putting the generic implementations in a separate
 nested namespace, we will be to call them as follows:
 
 ```
 namespace __llvm_libc {