common/Makefile: Add new symbol CONFIG_SPL_ENV_SUPPORT for environment in SPL

There will need the environment in SPL for reasons other than network
support (in particular, hwconfig contains info for how to set up DDR).

Add a new symbol CONFIG_SPL_ENV_SUPPORT to replace CONFIG_SPL_NET_SUPPORT
for environment in common/Makefile.

Signed-off-by: Ying Zhang <b40530@freescale.com>
Reviewed-by: Tom Rini <trini@ti.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/include/configs/a3m071.h b/include/configs/a3m071.h
index e9af825..8f29229 100644
--- a/include/configs/a3m071.h
+++ b/include/configs/a3m071.h
@@ -426,6 +426,7 @@
 #define CONFIG_SPL_BSS_MAX_SIZE		(64 << 10)
 
 #define CONFIG_SPL_OS_BOOT
+#define CONFIG_SPL_ENV_SUPPORT
 /* Place patched DT blob (fdt) at this address */
 #define CONFIG_SYS_SPL_ARGS_ADDR	0x01800000