auxdisplay: charlcd: deduplicate simple_strtoul()

auxdisplay: charlcd: deduplicate simple_strtoul()

Like in commit 8b2303de399f ("serial: core: Fix handling of options
after MMIO address") we may use simple_strtoul() which in comparison to
kstrtoul() can do conversion in-place without additional and unnecessary
code to be written.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andy Shevchenko <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Mans Rullgard <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>