staging:iio:adxrs450: Don't split string across multiple lines

This is one of the exceptions to the 80 chars per line rule since breaking the
string in half it badly affects the grep-ability.

Fixes the following checkpatch warning:
	WARNING: quoted string split across lines
	#203: FILE: staging/iio/gyro/adxrs450_core.c:203:
		+		dev_warn(&st->us->dev, "The initial power on response "
		+			 "is not correct! Restart without reset?\n");

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>