kernel-doc: include line numbers for function prototypes

This should solve bad error reports like this one:

	./include/linux/iio/iio.h:0: WARNING: Unknown target name: "devm".
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/56eed0ba50cd726236acd12b11b55ce54854c5ea.1599660067.git.mchehab+huawei@kernel.orgSigned-off-by: NJonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -1594,6 +1594,8 @@ sub dump_function($$) {
     my $file = shift;
     my $noret = 0;
 
+    print_lineno($.);
+
     $prototype =~ s/^static +//;
     $prototype =~ s/^extern +//;
     $prototype =~ s/^asmlinkage +//;