sh: Add a command line option for disabling I/O trapping.

This adds a 'noiotrap' kernel command line option to permit disabling of
I/O trapping. This is mostly useful for running on emulators where the
physical device limitations are not an issue.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

Documentation/kernel-parameters.txt

@@ -1544,6 +1544,8 @@ and is between 256 and 4096 characters. It is defined in the file
 			Valid arguments: on, off
 			Default: on
 
+	noiotrap	[SH] Disables trapped I/O port accesses.
+
 	noirqdebug	[X86-32] Disables the code which attempts to detect and
 			disable unhandled interrupt sources.