env: Add CONFIG_SYS_RELOC_GD_ENV_ADDR symbol

Today in initr_reloc_global_data() we use some non-obvious tests to
determine if we need to relocate the env_addr within gd or not.  In
order to facilitate migration of other symbols to Kconfig we need to
introduce a new symbol for this particular use case.

Cc: Wolfgang Denk <wd@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/bcm958712k_defconfig b/configs/bcm958712k_defconfig
index cba7f76..3b584fc 100644
--- a/configs/bcm958712k_defconfig
+++ b/configs/bcm958712k_defconfig
@@ -7,6 +7,7 @@
 CONFIG_BOOTDELAY=5
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SYS_PROMPT="u-boot> "
+CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_CONS_INDEX=4
 CONFIG_SYS_NS16550=y
 CONFIG_OF_LIBFDT=y