mtd: rawnand: Add a helper to clarify the interface configuration

stable inclusion
from stable-v5.10.137
commit c91e5215a4136c33fde9b9688643dbac72139d9b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c91e5215a4136c33fde9b9688643dbac72139d9b



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[ Upstream commit 961965c4 ]

Name it nand_interface_is_sdr() which will make even more sense when
nand_interface_is_nvddr() will be introduced.

Use it when relevant.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-2-miquel.raynal@bootlin.com


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>