exynos: config: enable arch memcpy and arch memset

exynos: config: enable arch memcpy and arch memset

This commit enables the following configs:
- CONFIG_USE_ARCH_MEMCPY
- CONFIG_USE_ARCH_MEMSET
This increases the performance of memcpy/memset
and also reduces the boot time.

This was tested on Trats2.
A quick test with trace. Boot time from start to main_loop() entry:
- ~1527ms - before this change (arch memset enabled for .bss clear)
- ~1384ms - after this change

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Akshay Saraswat <akshay.s@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Sjoerd Simons <sjoerd.simons@collabora.co.uk>