msun: Fix some old typos.

Seen in a posting from July 27 by "CM Graff" in musl-libc.

lib/msun/ld128/e_powl.c

@@ -32,7 +32,7 @@
  *	1. Compute and return log2(x) in two pieces:
  *		log2(x) = w1 + w2,
  *	   where w1 has 113-53 = 60 bit trailing zeros.
- *	2. Perform y*log2(x) = n+y' by simulating muti-precision
+ *	2. Perform y*log2(x) = n+y' by simulating multi-precision
  *	   arithmetic, where |y'|<=0.5.
  *	3. Return x**y = 2**n*exp(y'*log2)
  *

lib/msun/src/k_rem_pio2.c

@@ -52,7 +52,7 @@ __FBSDID("$FreeBSD$");
  *			64-bit  precision	2
  *			113-bit precision	3
  *		The actual value is the sum of them. Thus for 113-bit
- *		precison, one may have to do something like:
+ *		precision, one may have to do something like:
  *
  *		long double t,w,r_head, r_tail;
  *		t = (long double)y[2] + (long double)y[1];