power: supply: sbs-battery: only return health when battery present

when the battery is set to sbs-mode and  no gpio detection is enabled
"health" is always returning a value even when the battery is not present.
All other fields return "not present".
This leads to a scenario where the driver is constantly switching between
"present" and "not present" state. This generates a lot of constant
traffic on the i2c.

This commit changes the response of "health" to an error when the battery
is not responding leading to a consistent "not present" state.

Fixes: 76b16f4c ("power: supply: sbs-battery: don't assume MANUFACTURER_DATA formats")
Cc: <stable@vger.kernel.org>
Signed-off-by: Michael Nosthoff <committed@heine.so>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>