TPL: TM2: f_thor: fix wrong size caused by casting s32 to u64

TPL: TM2: f_thor: fix wrong size caused by casting s32 to u64

Currently, in arm64 environment, thor download for a file more than
2GB size is failed because requested file size is not properly set.
It is because of assignment of a signed value to a bigger unsigned
type for the size of a file. So this patch fixes wrong size casting.
This also fixes to print debug information about the requested file
size with casted variable.

Change-Id: Id0e67035be05b0df346a8bb0ea17b5ba3e40e8f2
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>