It is known that MSI interrupts - while working quite well so far - can
still cause issues on some hardware platforms (causing I2C timeouts due
to unhandled interrupts). The msi variable/option is set to 1 by default.
So, add a Kconfig option prefixed with "EXPERIMENTAL" that will control
the default value of that modparam, defaulting to off for a better
user experience and (guaranteed) stable operation "per default".

Cc: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Tested-by: Richard Scobie <r.scobie@clear.net.nz>
Tested-by: Jasmin Jessich <jasmin@anw.at>
Tested-by: Dietmar Spingler <d_spingler@freenet.de>
Tested-by: Manfred Knick <Manfred.Knick@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>