documentation: Fix spelling of "operators"

o	Avoid cancellation when using the "+" and "-" infix arithmetic

	operators.  For example, for a given variable "x", avoid

	"(x-x)".  There are similar arithmetic pitfalls from other

	arithmetic operatiors, such as "(x*0)", "(x/(x+1))" or "(x%1)".

	arithmetic operators, such as "(x*0)", "(x/(x+1))" or "(x%1)".

	The compiler is within its rights to substitute zero for all of

	these expressions, so that subsequent accesses no longer depend

	on the rcu_dereference(), again possibly resulting in bugs due