soc: qti_battery_debug: Remove CONFIG_DEBUG_FS dependency

As a preparatory move to adding device attributes to the battery_debug
device, remove the dependency on DEBUG_FS for driver enablement and add
config guards in the driver instead.

Change-Id: I8fcb385a583564935ce472416552e25ca79f4a84
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>