Document and enable the linux_spi driver

The linux_spi driver is now enabled by default on Linux.
A man page entry and a line in --list-supported output have been added.

Corresponding to flashrom svn r1498.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/print.c b/print.c
index b4900c3..f8a949b 100644
--- a/print.c
+++ b/print.c
@@ -527,6 +527,11 @@
 	       programmer_table[PROGRAMMER_SATAMV].name);
 	print_supported_pcidevs(satas_mv);
 #endif
+#if CONFIG_LINUX_SPI == 1
+	msg_ginfo("\nSupported devices for the %s programmer:\n",
+	       programmer_table[PROGRAMMER_LINUX_SPI].name);
+	msg_ginfo("Device files /dev/spidev*.*\n");
+#endif
 }
 
 #if CONFIG_INTERNAL == 1