openblas: enable ARM-specific optimizations

openblas: enable ARM-specific optimizations

OpenBLAS allows to specify per-family CPU optimizations during build stage.
This package supports manual specification of a family during configuration.
This commit adds automatic detection of target family, while keeping manual
override as a backup.

Automatically detected ARM families:
 - Cortex-A9 without NEON
 - Cortex-A9 with NEON
 - Cortex-A15
 - Cortex-A53
 - Cortex-A72

Signed-off-by: krant <aleksey.vasilenko@gmail.com>