sfc: replace min/max nesting with clamp()

sfc: replace min/max nesting with clamp()

The clamp() macro explicitly expresses the intent of constraining
a value within bounds.Therefore, replacing min(max(a, b), c) with
clamp(val, lo, hi) can improve code readability.

Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Reviewed-by: Joe Damato <joe@dama.to>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://patch.msgid.link/20250812065026.620115-1-zhao.xichao@vivo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>