mtd: nand: raw: denali: Wait for reset completion status

Fixed delay 200us is not working in certain platforms. Change to
poll for reset completion status to have more reliable reset process.

Controller will set the rst_comp bit in intr_status register after
controller has completed its reset and initialization process.

Tested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Radu Bacrau <radu.bacrau@intel.com>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>