The nds32 architecture will use physical memory when interrupt or
exception comes and it will use the setting of NTC0-4. The original
implementation didn't consider the DRAM start address may start from 1GB,
2GB or 3GB to cause this issue. It will write the data to DRAM if it is
running in physical address however kernel will read the data with
virtaul address through data cache. In this case, the data of DRAM is
latest.

This fix will set the correct cacheability to let kernel write/read the
latest data in cache instead of DRAM.

Signed-off-by: Greentime Hu <greentime@andestech.com>

This patch includes the kernel startup code. It can get dtb pointer
passed from bootloader. It will create a temp mapping by tlb
instructions at beginning and goto start_kernel.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>