usb: host: ehci: Make use of dma_pool_zalloc() instead of dma_pool_alloc/memset()

Replacing dma_pool_alloc/memset() with dma_pool_zalloc()
to simplify the code.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20211018131645.434-1-caihuoqing@baidu.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>