mtd: parsers: qcom: Fix kernel panic on skipped partition

In the event of a skipped partition (case when the entry name is empty)
the kernel panics in the cleanup function as the name entry is NULL.
Rework the parser logic by first checking the real partition number and
then allocate the space and set the data for the valid partitions.

The logic was also fundamentally wrong as with a skipped partition, the
parts number returned was incorrect by not decreasing it for the skipped
partitions.

Fixes: 803eb124

 ("mtd: parsers: Add Qcom SMEM parser")
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220116032211.9728-1-ansuelsmth@gmail.com