usb: gadget: f_thor: Allocate request up to THOR_PACKET_SIZE

Allocate request up to THOR_PACKET_SIZE not the ep0->maxpacket
as the descriptors data depend on the number of descriptors
and this 64 bytes were not enough and the buffer might overflow
which results in memalign failures later.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>