mtd: rawnand: qcom: Clear buf_count and buf_start in raw read

Initialize buf_count and buf_start to 0 before starting the
raw read. If we will not initialize then read staus will get
updated with wrong value and we will see failure for even
successful raw read transaction.

Signed-off-by: Sricharan Ramabadhran <quic_srichara@quicinc.com>
Signed-off-by: Md Sadre Alam <quic_mdalam@quicinc.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230818145101.23825-3-quic_mdalam@quicinc.com