Revert "sandbox: Disable I2C emulators in SPL"

With recent changes this can be supported again. Add it back.

This reverts commit d85f2c4f2970d0ec2f5f075de734afd11200d153.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index 4c02052..1ac7e02 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -103,6 +103,7 @@
 CONFIG_SPL_SYSCON=y
 CONFIG_DEVRES=y
 CONFIG_DEBUG_DEVRES=y
+# CONFIG_SPL_SIMPLE_BUS is not set
 CONFIG_ADC=y
 CONFIG_ADC_SANDBOX=y
 CONFIG_AXI=y