div64: Correct inline documentation for `do_div'

Correct inline documentation for `do_div', which is a function-like
macro the `n' parameter of which has the semantics of a C++ reference:
it is both read and written in the context of the caller without an
explicit dereference such as with a pointer.

In the C programming language it has no equivalent for proper functions,
in terms of which the documentation expresses the semantics of `do_div',
but substituting a pointer in documentation is misleading, and using the
C++ notation should at least raise the reader's attention and encourage
to seek explanation even if the C++ semantics is not readily understood.

While at it observe that "semantics" is an uncountable noun, so refer to
it with a singular rather than plural verb.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

include/asm-generic/div64.h

@@ -8,12 +8,14 @@
  * Optimization for constant divisors on 32-bit machines:
  * Copyright (C) 2006-2015 Nicolas Pitre
  *
- * The semantics of do_div() are:
+ * The semantics of do_div() is, in C++ notation, observing that the name
+ * is a function-like macro and the n parameter has the semantics of a C++
+ * reference:
  *
- * uint32_t do_div(uint64_t *n, uint32_t base)
+ * uint32_t do_div(uint64_t &n, uint32_t base)
  * {
- * 	uint32_t remainder = *n % base;
- * 	*n = *n / base;
+ * 	uint32_t remainder = n % base;
+ * 	n = n / base;
  * 	return remainder;
  * }
  *