driver/mtd/IFC:Wait tWB time, poll R/B before command execution

driver/mtd/IFC:Wait tWB time, poll R/B before command execution

IFC_FIR_OP_CMD0 issues command for execution without checking flash
readiness. It may cause problem if flash is not ready. Instead use
IFC_FIR_OP_CW0 which Wait for tWB time and poll R/B to return high or
time-out, before issuing command.

NAND_CMD_READID command implemention does not fulfill above requirement. So
update its programming.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Hemant Nautiyal <hemant.nautiyal@freescale.com>