USB: core: hub.c: Fix bug in accessing freed memory

Current driver is accessing the buffer memory after it is freed.
This could result in getting wrong value and might could cause
memory corruption. Hence fix this issue by taking idvendor
value into a variable before freeing it.

CRs-Fixed: 550211
Change-Id: I271dbf3518e7b6e0d30c684bd05c835945de0950
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>