Remove exit calls from print_supported_chips

Propagate the error code using return values instead, but let cli_classic.c
still decide the ultimate return value of the process.
Also, remove setting the ret value again after print_supported_wiki() - 
success is the default.

Corresponding to flashrom svn r1614.

Signed-off-by: Niklas Söderlund <niso@kth.se>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/flash.h b/flash.h
index 4913536..0bb6c2b 100644
--- a/flash.h
+++ b/flash.h
@@ -214,7 +214,7 @@
 
 /* print.c */
 char *flashbuses_to_text(enum chipbustype bustype);
-void print_supported(void);
+int print_supported(void);
 void print_supported_wiki(void);
 
 /* flashrom.c */