This patch splits hmc5843.c to multiple files - the interface-agnostic
hmc5843_core.c, i2c specific hmc5843_i2c.c and header file hmc5843.h. This is
another step to add support of SPI-enabled hmc5983.
Signed-off-by: Josef Gajdusek <atx@atx.name> Signed-off-by: Jonathan Cameron <jic23@kernel.org>