ARM: bcm: clean up SMC code

This patch just does some simple cleanup in "bcm_kona_smc.c":
    - Get rid of the secure_bridge_data structure.  Instead, just
      define two globals that record the physical and virtual
      addresses of the SMC arguments buffer.  Use "buffer" instead
      of "bounce" in their names.  Drop of the erroneous __iomem
      annotation for the physical address.
    - Get rid of the initialized flag and just use a non-null buffer
      address to indicate that.
    - Get the size of the memory region when fetching the SMC
      arguments buffer location from the device tree.  Use it to
      call ioremap() directly rather than requiring of_iomap() to
      go look it up again.
    - Do some additional validation on that memory region size.
    - Flush caches unconditionally in __bcm_kona_smc(); nothing
      supplies SSAPI_BRCM_START_VC_CORE as a service id.
    - Drop a needless initialization of "rc" in __bcm_kona_smc().

It also deletes most of the content of "bcm_kona_smc.h" because it's
never actually used and is of questionable value anyway.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Tim Kryger <tim.kryger@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Matt Porter <mporter@linaro.org>