ath10k: sdio: remove redundant check in for loop

The for loop checks whether cur_section is NULL on every iteration, but
we know it can never be NULL as there is another check towards the
bottom of the loop body. Refactor to avoid this unnecessary check.

Also, increment the variable i inline for clarity

Addresses-Coverity: 1496984 ("Null pointer dereferences)
Suggested-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200916165748.20927-1-alex.dewar90@gmail.com