Convert CONFIG_ENV_IS_IN_REMOTE to Kconfig

This converts the following to Kconfig:
   CONFIG_ENV_IS_IN_REMOTE

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/T2081QDS_SRIO_PCIE_BOOT_defconfig b/configs/T2081QDS_SRIO_PCIE_BOOT_defconfig
index 19c48a8..a49aff5 100644
--- a/configs/T2081QDS_SRIO_PCIE_BOOT_defconfig
+++ b/configs/T2081QDS_SRIO_PCIE_BOOT_defconfig
@@ -6,6 +6,7 @@
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="SRIO_PCIE_BOOT_SLAVE,SYS_TEXT_BASE=0xFFF40000"
+CONFIG_ENV_IS_IN_REMOTE=y
 CONFIG_BOOTDELAY=10
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMLS is not set