power: smb5-lib: Fix reporting of DIE_HEALTH

Report die health status as unknown if no charging adaptor is connected.

Use a helper function to determine whether any valid input adaptor is
connected or not, and also update other sites that make use of this
logic.

Change-Id: I08f3cbad6036f9230e74caa2c86da7e8f68f0677
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>