iio:accel:bma180: Fix use of true when should be iio_shared_by enum

Given a value of 1 corresponds to IIO_SHARE_BY_TYPE I have replaced
it with that.  Should cause no functional change.

Fixes: fdadbce0 ("iio: add Bosch BMA180 acceleration sensor driver")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Matt Ranostay <matt.ranostay@konsulko.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Oleksandr Kravchenko <o.v.kravchenko@globallogic.com>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Jonathan Bakker <xc-racer2@live.ca>
Link: https://lore.kernel.org/r/20200913121227.764626-1-jic23@kernel.org