Prefer 'kstrtoX()' family of functions over 'sscanf()' to convert
strings to integers and always check results of the conversions.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230725060531.72968-6-dmantipov@yandex.ru