ABI: sysfs-class-mux: use wildcards on What definitions

An "N" upper letter is not a wildcard, nor can easily be identified
by script, specially since the USB sysfs define things like.
bNumInterfaces. Use, instead, <N>, in order to let script/get_abi.pl
to convert it into a Regex.
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/7e8ff8601d5b44b76c5c7f77b6dcf3b1d45bc5be.1631782432.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-class-mux

@@ -7,7 +7,7 @@ Description:
 		Framework and provides a sysfs interface for using MUX
 		controllers.
 
-What:		/sys/class/mux/muxchipN/
+What:		/sys/class/mux/muxchip<N>/
 Date:		April 2017
 KernelVersion:	4.13
 Contact:	Peter Rosin <peda@axentia.se>