Remove parameter from nyx_system_erase_partition()

:Release Notes:
The nyx_system_erase_partition method API has changed to avoid buffer
overflow errors.

This API change takes nyx-lib (and its modules) to v6.0.0 .

:Detailed Notes:
The nyx_system_erase_partition method had an "error message" parameter
of type `char *`. The original intent was to return an error message
through the pointer. However, without a buffer length parameter, there
is simply no safe way to implement that.

Alternatives were to either change it a 'char **' and return a
dynamically allocated buffer (which raises the possibility of memory
leaks), add a buffer length parameter (which seems a bit unnecessary
overhead for an unlikley error condition), or simply delete the
parameter from the API.

As the method already has an error code return value, the third option
was taken.

:Testing Performed:
Currently, nothing is using this method, so the only testing required
is clean compilation.

:QA Notes:

:Issues Addressed:
[GF-37730] Provide implementation of Nyx System module to support
           factory reset

Open-webOS-DCO-1.0-Signed-off-by: Keith Derrick <keith.derrick@lge.com>
Change-Id: Icd9be116e99255da89dd1d504555fa2913971e50
Reviewed-on: https://g2g.palm.com/3562
Reviewed-by: Build Verification
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>