ARM: ux500: do not directly dereference __iomem

ARM: ux500: do not directly dereference __iomem

Sparse reports that calling add_device_randomness() on `uid` is a
violation of address spaces. And indeed the next usage uses readl()
properly, but that was left out when passing it toadd_device_
randomness(). So instead copy the whole thing to the stack first.

Fixes: 4040d10a3d44 ("ARM: ux500: add DB serial number to entropy pool")
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/202210230819.loF90KDh-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20221108123755.207438-1-Jason@zx2c4.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>