arm: socfpga: arria10: Enable cache driver in SPL

Adding "u-boot,dm-pre-reloc" and enable CONFIG_SPL_CACHE
to enable cache driver in SPL.

This fixed error below in SPL:
cache controller driver NOT found!

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
diff --git a/arch/arm/mach-socfpga/Kconfig b/arch/arm/mach-socfpga/Kconfig
index 38d6c1b..a3699e8 100644
--- a/arch/arm/mach-socfpga/Kconfig
+++ b/arch/arm/mach-socfpga/Kconfig
@@ -46,6 +46,7 @@
 	bool
 	select SPL_ALTERA_SDRAM
 	select SPL_BOARD_INIT if SPL
+	select SPL_CACHE if SPL
 	select CLK
 	select SPL_CLK if SPL
 	select DM_I2C