m25p80: Initial implementation of SPI flash device

Added device model for m25p80 style SPI flash family.

Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
index f335a72..2f1a5c9 100644
--- a/default-configs/arm-softmmu.mak
+++ b/default-configs/arm-softmmu.mak
@@ -22,6 +22,7 @@
 CONFIG_MAX111X=y
 CONFIG_SSI=y
 CONFIG_SSI_SD=y
+CONFIG_SSI_M25P80=y
 CONFIG_LAN9118=y
 CONFIG_SMC91C111=y
 CONFIG_DS1338=y