lib: cleanup kstrto*() usage

[ Upstream commit 506dfc99 ]

Use proper conversion functions.  kstrto*() variants exist for all
standard types.

Link: https://lkml.kernel.org/r/20201122123410.GB92364@localhost.localdomain


Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stable-dep-of: 4acfe3df ("test_firmware: prevent race conditions by a correct implementation of locking")
Signed-off-by: Sasha Levin <sashal@kernel.org>