usb: composite: Fix reporting MaxPower as 0x71 instead of 0x70

USB device is reporting MaxPower as 0x71 (i.e. 904mA) when enumerated
into USB super speed mode. Few host may complain about not able to
supply enough power to connected device. Hence fix this issue by
reporting MaxPower as 0x70 (i.e. 896 mA) which is within allowed
current draw limit (i.e. 900mA) of USB specification.

CRs-Fixed: 2217005
Change-Id: I4e7a1b4bb5aee8abdcd49d101face5dc7cf36830
Signed-off-by: Mayank Rana <mrana@codeaurora.org>