Documentation/kcov: define `ip' in the example

The example code uses the variable `ip' but never declares it.

Declare `ip' as a 64bit variable which is the same type as the array
from which it loads its value.

Link: https://lkml.kernel.org/r/20210923164741.1859522-3-bigeasy@linutronix.de
Link: https://lore.kernel.org/r/20210830172627.267989-3-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Marco Elver <elver@google.com>
Tested-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Sebastian Andrzej Siewior

Documentation/dev-tools/kcov.rst

@@ -178,6 +178,8 @@ Comparison operands collection is similar to coverage collection:
 	/* Read number of comparisons collected. */
 	n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED);
 	for (i = 0; i < n; i++) {
+		uint64_t ip;
+
 		type = cover[i * KCOV_WORDS_PER_CMP + 1];
 		/* arg1 and arg2 - operands of the comparison. */
 		arg1 = cover[i * KCOV_WORDS_PER_CMP + 2];