perl-sys-cpu: improve Config.in description

And also fix a check-package warning due to the lack of upstream
webpage:

package/perl-sys-cpu/Config.in:5: empty line at end of file

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/perl-sys-cpu/Config.in

@@ -1,5 +1,5 @@
 config BR2_PACKAGE_PERL_SYS_CPU
 	bool "perl-sys-cpu"
 	help
-	  perl-sys-cpu
-
+	  Perl module for getting information about the system CPU
+	  (Sys::CPU).