This patch adds implementation of rand library based on hardware random
number generator of security subsystem in Exynos SOC.

This library includes:
- srand()  - used for seed hardware block
- rand()   - returns random number
- rand_r() - the same as above with given seed

which depends on CONFIG_EXYNOS_ACE_SHA and CONFIG_LIB_HW_RAND.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
cc: Akshay Saraswat <akshay.s@samsung.com>
cc: ARUN MANKUZHI <arun.m@samsung.com>
cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Michael Walle <michael@walle.cc>
Cc: Tom Rini <trini@ti.com>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>