scripts: kernel-doc: accept negation like !@var

On a few places, it sometimes need to indicate a negation of a
parameter, like:

	!@fshared

This pattern happens, for example, at:

	kernel/futex.c

and it is perfectly valid. However, kernel-doc currently
transforms it into:

	!**fshared**

This won't do what it would be expected.

Fortunately, fixing the script is a simple matter of storing
the "!" before "@" and adding it after the bold markup, like:

	**!fshared**
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/0314b47f8c3e1f9db00d5375a73dc3cddd8a21f2.1586881715.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -213,6 +213,7 @@ my $type_constant = '\b``([^\`]+)``\b';
 my $type_constant2 = '\%([-_\w]+)';
 my $type_func = '(\w+)\(\)';
 my $type_param = '\@(\w*((\.\w+)|(->\w+))*(\.\.\.)?)';
+my $type_param_ref = '([\!]?)\@(\w*((\.\w+)|(->\w+))*(\.\.\.)?)';
 my $type_fp_param = '\@(\w+)\(\)';  # Special RST handling for func ptr params
 my $type_fp_param2 = '\@(\w+->\S+)\(\)';  # Special RST handling for structs with func ptr params
 my $type_env = '(\$\w+)';
@@ -237,6 +238,7 @@ my @highlights_man = (
                       [$type_typedef, "\\\\fI\$1\\\\fP"],
                       [$type_union, "\\\\fI\$1\\\\fP"],
                       [$type_param, "\\\\fI\$1\\\\fP"],
+                      [$type_param_ref, "\\\\fI\$1\$2\\\\fP"],
                       [$type_member, "\\\\fI\$1\$2\$3\\\\fP"],
                       [$type_fallback, "\\\\fI\$1\\\\fP"]
 		     );
@@ -258,7 +260,7 @@ my @highlights_rst = (
                        [$type_union, "\\:c\\:type\\:`\$1 <\$2>`"],
                        # in rst this can refer to any type
                        [$type_fallback, "\\:c\\:type\\:`\$1`"],
-                       [$type_param, "**\$1**"]
+                       [$type_param_ref, "**\$1\$2**"]
 		      );
 my $blankline_rst = "\n";