misc: bh1780: Introduce the use of devm_kzalloc

This patch introduces the use of devm_kzalloc and does away with the
kfrees in the probe and remove functions. A label and the kfree
being called on the return path of failure on i2c_check_functionality,
which is completely unnecessary and removed. The NULL assignment of
ddata is no longer required is also done away with.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>