mtd: devices: elm: Low power transition support

In low power modes of AM335X platforms, peripherals power is cut off.
This patch supports low power sleep transition support for ELM driver.

Signed-off-by: Philip Avinash <avinashphilip@ti.com>
mtd: nand: omap2: bch default y

Signed-off-by: Philip Avinash <avinashphilip@ti.com>