usb: core: driver: Use kmalloc_array

Use kmalloc_array instead of kmalloc to allocate memory for an array.
Also, remove the dev_warn for a memory leak, making the if check more
sleek.

Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>