net: ti: icss-iep: Move icss_iep structure

Move icss_iep structure definition and to icss_iep.h file so that the
structure members can be used / accessed by all icssg driver files.

Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://patch.msgid.link/20240911081603.2521729-2-danishanwar@ti.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>