mux: remove usage of the deprecated ida_simple_xx() API

mux: remove usage of the deprecated ida_simple_xx() API

ida_alloc() and ida_free() should be preferred to the deprecated
ida_simple_get() and ida_simple_remove().

This is less verbose.

Link: https://lkml.kernel.org/r/f82e013abe4c71f1c7d06819f96472f298acdcf3.1713089554.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Peter Rosin <peda@axentia.se>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>