The battery/charging level and status is reported only if the related
reporting flag in register 0x00 is enabled by the host. The
"Battery/Charging Level" byte indicates the battery level if the
"Charging State" indicates 0x00 ("Not Charging"). If "Charging State"
indicates 0x21 to 0x23 ("Charging"), the "Battery/Charging Level" byte
indicates the level of charging.

10 ix 07 r0 r1 r2 00
r0 -> Battery/Charging Level
                  0x00 = Reserved/Unknown
                  0x01 = Critical
                  0x02 = Critical (legacy value, don't use)
                  0x03 = Low
                  0x04 = Low (legacy value, don't use)
                  0x05 = Good
                  0x06 = Good (legacy value, don't use)
                  0x07 = Full
                  0x08..0xFF = Reserved
r1 ->  Charging state
                  0x00 = Not charging
                  0x01..0x1F = Reserved (not charging)
                  0x20 = Unknown charging state
                  0x21 = Charging
                  0x22 = Charging complete
                  0x23 = Charging error
                  0x24..0xFF = Reserved