pickit2_spi: use ordinary USB devs array

Even though there is currently only one USB device ID in the wild using our
standard way to define the devices creates nicer output for -L and -z.

Corresponding to flashrom svn r1941.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

programmer.h

@@ -499,6 +499,7 @@ int mstarddc_spi_init(void);
 /* pickit2_spi.c */
 #if CONFIG_PICKIT2_SPI == 1
 int pickit2_spi_init(void);
+extern const struct dev_entry devs_pickit2_spi[];
 #endif
 
 /* rayer_spi.c */