mk: restrict CPU flags list

mk: restrict CPU flags list

When compiling each file, the CPU flags are given as RTE_MACHINE_CPUFLAG_*
and in the list RTE_COMPILE_TIME_CPUFLAGS.

RTE_MACHINE_CPUFLAG_* are used to check the CPU features when compiling.

The list RTE_COMPILE_TIME_CPUFLAGS is used only to check the CPU at
runtime in the function rte_cpu_check_supported(). So it is not needed to
define this list for every files.
That's why RTE_COMPILE_TIME_CPUFLAGS is removed from the common variable
MACHINE_CFLAGS and is added only to the CFLAGS of eal_common_cpuflags.c.

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>