hwpstate_amd: Fix compile error

Add parentheses between OR and AND operator to pass the compiler check.

Approved by:    lwhsu (mentor)
Fixes:  3e6e4e4a0d ("hwpstate: add CPPC support for pstate driver on AMD")
MFC aftert:     2 weeks
Differential Revision: https://reviews.freebsd.org/D54465

sys/x86/cpufreq/hwpstate_amd.c

@@ -118,7 +118,7 @@
 #define	BITS_VALUE(bits, num)			(((num) & (bits)) >> (ffsll((bits)) - 1))
 #define	BITS_WITH_VALUE(bits, val)		((uintmax_t)(val) << (ffsll((bits)) - 1))
 #define	SET_BITS_VALUE(var, bits, val) \
-	((var) = (var) & ~(bits) | BITS_WITH_VALUE((bits), (val)))
+	((var) = ((var) & ~(bits)) | BITS_WITH_VALUE((bits), (val)))
 
 #define	HWPSTATE_DEBUG(dev, msg...)			\
 	do {						\