Move generic ipi_mb functions to common files

ipi_mb functions can be used for other Xilinx platform.
Move it to common file from platform specific files.

Signed-off-by: Tejas Patel <tejas.patel@xilinx.com>
Reviewed-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Jolly Shah <jollys@xilinx.com>