staging: unisys: visornic: no need to check debugfs return values

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Clean up the visornic driver code by not caring about the value of
debugfs calls.  This ends up removing a number of lines of code that are
not needed.

Cc: David Kershner <david.kershner@unisys.com>
Cc: Tim Sell <timothy.sell@unisys.com>
Cc: David Binder <david.binder@unisys.com>
Cc: Sameer Wadgaonkar <sameer.wadgaonkar@unisys.com>
Cc: Charles Daniels <cdaniels@fastmail.com>
Cc: sparmaintainer@unisys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>