boards: nordic: nRF54L15DK: Add basic support for the L05 and L10 ICs

The nRF54L05 and nRF54L10 are identical to the nRF54L15 except for their
memory sizes. Add support for emulating those ICs on the nRF54L15DK.
This commit only adds support for the main application core. Support for
the FLPR core may be added later.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>