POWER_DESC_MAX_SIZE is unused, remove it.

Link: https://lore.kernel.org/r/20201207190137.6858-2-huobean@gmail.comAcked-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>