mtd: phram: Module parameters add writable permissions

The phram code implements managing multiple devices through a linked
list.
However, due to the module parameter permission of 0, the
/sys/module/phram/parameters/phram interface is missing.
The command line arguments in insmod can only create one device.

Therefore, add writable permissions to the module parameters, create
/sys/module/phram/parameters/phram interface, and create multi-device
support.

Signed-off-by: Xiaoming Ni <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

drivers/mtd/devices/phram.c

···
 #endif
 }
 
-module_param_call(phram, phram_param_call, NULL, NULL, 000);
+module_param_call(phram, phram_param_call, NULL, NULL, 0200);
 MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>\"");