Makefile: Add support of CONFIG_SPL_FSL_PBL

Objective of this target to have concatenate binary having
 - SPL binary in PBL command format
 - U-boot binary

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/README b/README
index 52283e2..49dcd37 100644
--- a/README
+++ b/README
@@ -505,6 +505,10 @@
 		PBI commands can be used to configure SoC before it starts the execution.
 		Please refer doc/README.pblimage for more details
 
+		CONFIG_SPL_FSL_PBL
+		It adds a target to create boot binary having SPL binary in PBI format
+		concatenated with u-boot binary.
+
 		CONFIG_SYS_FSL_DDR_BE
 		Defines the DDR controller register space as Big Endian