sensor: lis2dh: fix SPI burst transfers

After switching to new SPI API there is no need to reserve first dummy
byte in buffer and ignore that in application later on. Instead two
buffers can be specified, which is how it is done already in lis2dh
driver. The problem is that dummy byte is still part of the buffer, but
it clearly should no longer be. As an example we write 0x7 (bits to
enable XYZ axes) into CTRL2 instead of CTRL1 register. When reading
measurements on the other hand we have filled buffer starting from 0,
instead of 1 as the driver code has expected.

Fix driver in all places that use burst transfers by removing first
dummy byte from input/output buffer.

Fixes: 2f7e6b6d ("drivers/sensors: Switch lis2dh driver to new SPI
  API")
Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>