mtd:rawnand: brcmnand: Fix PM resume crash

This change fixes crash observed on PM resume. This bug
was introduced in the change made for flash-edu support.

Fixes: a5d53ad2

 ("mtd: rawnand: brcmnand: Add support for flash-edu for dma transfers")

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>