pwm: qti-lpg: Fix erroneous clearing of LUT

The memory allocated for the lookup table (LUT) is getting cleared even
when a valid nvmem and PBS configuration is detected. Fix this by
ensuring that this happens only when neither a LUT peripheral's address
nor a valid nvmem configuration is detected.

Fixes: 218908e8 ("pwm: pwm-qti-lpg: Refactor qpnp_lpg_parse_dt() for
readability").

Change-Id: I59467d46779e0a01bf0843863680ec2a8f85f2ce
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>