package/dovecot/Config.in: source argument needs quotation marks

Fixes the following error/warnings with kconfig from linux-6.9-rc5:

  package/dovecot/Config.in:36: syntax error
  package/dovecot/Config.in:36:warning: ignoring unsupported character '/'
  package/dovecot/Config.in:36:warning: ignoring unsupported character '/'
  package/dovecot/Config.in:36:warning: ignoring unsupported character '.'
  package/dovecot/Config.in:36: invalid statement

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/dovecot/Config.in

@@ -33,7 +33,7 @@ config BR2_PACKAGE_DOVECOT_SQLITE
 	help
 	  Enable SQLite support.
 
-source package/dovecot-pigeonhole/Config.in
+source "package/dovecot-pigeonhole/Config.in"
 
 endif # BR2_PACKAGE_DOVECOT