powerpc/pseries: Add ibm,set-dynamic-indicator RTAS call support

The RTAS call ibm,set-dynamic-indicator is used to set the new
indicator state identified by a location code. The current
implementation uses rtas_set_dynamic_indicator() API provided by
librtas library which allocates RMO buffer and issue this RTAS
call in the user space. But /dev/mem access by the user space
is prohibited under system lockdown.

This patch provides an interface with new ioctl
PAPR_DYNAMIC_INDICATOR_IOC_SET to the papr-indices character
driver and expose this interface to the user space that is
compatible with lockdown.

Refer PAPR 7.3.18 ibm,set-dynamic-indicator for more
information on this RTAS call.
-  User input parameters to the RTAS call: location code
   string, indicator token and new state

Expose these interfaces to user space with a /dev/papr-indices
character device using the following programming model:
 int fd = open("/dev/papr-indices", O_RDWR);
 int ret = ioctl(fd, PAPR_DYNAMIC_INDICATOR_IOC_SET,
		struct papr_indices_io_block)
  - The user space passes input parameters in papr_indices_io_block
    struct

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Tested-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250416225743.596462-5-haren@linux.ibm.com