The I2C-bus to the XPower AXP288 is shared between the Linux kernel and
the SoCs P-Unit. The P-Unit has a semaphore which the kernel must "lock"
before it may use the bus. This semaphore is automatically taken by the
I2C-bus-driver.

The retry on -EBUSY logic in fuel_gauge_reg_readb() likely was added to
deal with the I2C-bus-drive returning -EBUSY when it failed to take the
semaphore, but this really should never happen. The semaphore code even
has a WARN_ON(ret) to log a kernel backtrace if this does somehow happen,
when this happens something is seriously wrong and the system typically
freezes soon afterwards.

TL;DR: the regmap_read() should never fail with -EBUSY so the retries
are unnecessary.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>