mk: add crypto capability for armv8a and thunderx

mk: add crypto capability for armv8a and thunderx

armv8-a has optional CRYPTO extension which adds the
AES, PMULL, SHA1 and SHA2 capabilities. -march=armv8-a+crypto
enables code generation for the ARMv8-A architecture together
with the optional CRYPTO extensions.

Added the following flags to detect the corresponding
capability at compile time.
 * RTE_MACHINE_CPUFLAG_AES
 * RTE_MACHINE_CPUFLAG_PMULL
 * RTE_MACHINE_CPUFLAG_SHA1
 * RTE_MACHINE_CPUFLAG_SHA2

At run-time, the following flags can be used to detect the
capabilities.
 * RTE_CPUFLAG_AES
 * RTE_CPUFLAG_PMULL
 * RTE_CPUFLAG_SHA1
 * RTE_CPUFLAG_SHA2

Signed-off-by: Ashwin Sekhar T K <ashwin.sekhar@caviumnetworks.com>
Reviewed-by: Jan Viktorin <viktorin@rehivetech.com>