mtd: rawnand: qcom: Unmap sg_list and free desc within submic_descs()

There are two types of dma descriptors being used in this driver allocated
by, prepare_bam_async_desc() and prep_adm_dma_desc() helper functions.
These functions map and prepare the descriptors to be used for dma
transfers.

And all the descriptors are submitted inside the submit_descs() function.
Once the transfer completion happens, those descriptors should be unmapped
and freed as a part of cleanup.

Currently, free_descs() function is doing the said cleanup of descriptors.
But the callers of submit_descs() are required to call free_descs() in both
the success and error cases.

Since there are no other transactions need to be done after submit_descs(),
let's just move the contents of free_descs() inside submit_descs() itself.

This makes sure that the cleanup is handled within the submit_descs()
thereby offloading the cleanup part from callers.

While at it, let's also rename the return variable from "r" to "ret".

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230805174146.57006-8-manivannan.sadhasivam@linaro.org