mtd: rawnand: qcom: avoid write to unavailable register

SFLASHC_BURST_CFG is only available on older ipq NAND platforms, this
register has been removed when the NAND controller got implemented in
the qpic controller.

Avoid writing this register on devices which are based on qpic NAND
controller.

Fixes: dce84760 ("mtd: nand: qcom: Support for IPQ8074 QPIC NAND controller")
Cc: stable@vger.kernel.org
Signed-off-by: Sivaprakash Murugesan <sivaprak@codeaurora.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/1591948696-16015-2-git-send-email-sivaprak@codeaurora.org