checkstyle9: Allow a space between "*" and _*restrict

Before the change, we would get errors like this:

    ERROR: "foo * bar" should be "foo *bar"
    #369: FILE: foobar.c:369:
    +barbaz(char * __restrict s,

Reviewed by:		des, imp
Sponsored by:		Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D44911

tools/build/checkstyle9.pl

@@ -202,6 +202,7 @@ our $Sparse	= qr{
 # Notes to $Attribute:
 our $Attribute	= qr{
 			const|
+			_*restrict|
 			volatile|
 			QEMU_NORETURN|
 			QEMU_WARN_UNUSED_RESULT|