crypto: qat - replace the if statement with min()

Mark UWORD_CPYBUF_SIZE with U suffix to make its type the same
with words_num. Then replace the if statement with min() in
qat_uclo_wr_uimage_raw_page() to make code shorter.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: You Kangren <youkangren@vivo.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>