svc: Implement svcGetResourceLimitLimitValue()

This kernel service function retrieves the maximum allowable value for
a provided resource category for a given resource limit instance. Given
we already have the functionality added to the resource limit instance
itself, it's sufficient to just hook it up.

The error scenarios for this are:

1. If an invalid resource category type is provided, then ERR_INVALID_ENUM is returned.

2. If an invalid handle is provided, then ERR_INVALID_HANDLE is returned (bad thing goes in, bad thing goes out, as one would expect).

If neither of the above error cases occur, then the out parameter is
provided with the maximum limit value for the given category and success
is returned.