nxp: Cleanup some emulator related options.

- Drop the emulator CONFIG test from include/configs/ls1088ardb.h
- Migrate CONFIG_SYS_FSL_DDR_EMU to a select'able option in
  drivers/ddr/fsl/Kconfig

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/ddr/fsl/Kconfig b/drivers/ddr/fsl/Kconfig
index fe69bef..6a29b23 100644
--- a/drivers/ddr/fsl/Kconfig
+++ b/drivers/ddr/fsl/Kconfig
@@ -10,6 +10,12 @@
 	help
 	  Select Freescale Multi Mode DDR controller (MMDC).
 
+config SYS_FSL_DDR_EMU
+	bool
+	help
+	  Specify emulator support for DDR. Some DDR features such as deskew
+	  training are not available.
+
 if SYS_FSL_DDR || SYS_FSL_MMDC
 
 config SYS_FSL_DDR_BE