mtd: rawnand: brcmnand: skip DMA during panic write

mtd: rawnand: brcmnand: skip DMA during panic write

When oops_panic_write is set, the driver disables interrupts and
switches to PIO polling mode but still falls through into the DMA
path. DMA cannot be used reliably in panic context, so make the
DMA path an else branch to ensure only PIO is used during panic
writes.

Fixes: c1ac2dc34b51 ("mtd: rawnand: brcmnand: When oops in progress use pio and interrupt polling")
Signed-off-by: Kamal Dasu <kamal.dasu@broadcom.com>
Reviewed-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>