bus/fsl-mc: Cache the DPRC API version

bus/fsl-mc: Cache the DPRC API version

There are already firmware API commands that have multiple
versions. For each multiple version command, another command
to retrieve the API version is issued. This may introduce an important
overhead. The version does not change while the system is running,
so the DPRC API version can be safely cached.

Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
Link: https://lore.kernel.org/r/20200929085441.17448-6-diana.craciun@oss.nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>