stm32mp1: add check for presence of environment in boot device

For boot from flash, check presence of default environment to force
save env.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Tested-by: Pierre-Jean Texier <pjtexier@koncepto.io>

include/configs/stm32mp1.h

@@ -103,6 +103,7 @@
 	"if test ${boot_device} = serial || test ${boot_device} = usb;" \
 	"then stm32prog ${boot_device} ${boot_instance}; " \
 	"else " \
+		"run env_check;" \
 		"if test ${boot_device} = mmc;" \
 		"then env set boot_targets \"mmc${boot_instance}\"; fi;" \
 		"if test ${boot_device} = nand;" \
@@ -134,6 +135,9 @@
 	"ramdisk_addr_r=0xc4400000\0" \
 	"fdt_high=0xffffffff\0" \
 	"initrd_high=0xffffffff\0" \
+	"env_default=1\0"				\
+	"env_check=if test $env_default -eq 1;"\
+		" then env set env_default 0;env save;fi\0" \
 	STM32MP_BOOTCMD \
 	STM32MP_MTDPARTS \
 	BOOTENV