imx8ulp_evk: enable binman support

Enable binman support and add documentation for the
imx8ul-evk board.

Signed-off-by: Gary Bisson <bisson.gary@gmail.com>
diff --git a/arch/arm/mach-imx/imx8ulp/Kconfig b/arch/arm/mach-imx/imx8ulp/Kconfig
index 49ea252..fbca241 100644
--- a/arch/arm/mach-imx/imx8ulp/Kconfig
+++ b/arch/arm/mach-imx/imx8ulp/Kconfig
@@ -23,6 +23,7 @@
 
 config TARGET_IMX8ULP_EVK
 	bool "imx8ulp_evk"
+	select BINMAN
 	select IMX8ULP
 	select SUPPORT_SPL
 	select IMX8ULP_DRAM