[profile] Prevent potential division by zero

Limit the profile sample count to INT_MAX to avoid both signed
overflow and a potential division by zero when updating the stored
mean value.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/profile.c

 #include <stdint.h>
 #include <stdio.h>
 #include <strings.h>
+#include <limits.h>
 #include <assert.h>
 #include <ipxe/isqrt.h>
 #include <ipxe/profile.h>
 	 */
 	assert ( ( ( signed ) sample ) >= 0 );
 
-	/* Update sample count */
-	profiler->count++;
+	/* Update sample count, limiting to avoid signed overflow */
+	if ( profiler->count < INT_MAX )
+		profiler->count++;
 
 	/* Adjust mean sample value scale if necessary.  Skip if
 	 * sample is zero (in which case flsl(sample)-1 would