serial: sh-sci: Fix HSCIF RX sampling point adjustment

The calculation of the sampling point has min() and max() exchanged.
Fix this by using the clamp() helper instead.

Fixes: 63ba1e00 ("serial: sh-sci: Support for HSCIF RX sampling point adjustment")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Dirk Behme <dirk.behme@de.bosch.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>