libc/eglibc: Make eglibc 2.11 and 2.12 not experimental

I haven't noticed the usual experimental testers complain about eglibc
2.11 or 2.12 being unstable. So stop marking them as experimental.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>

# Alpha specific configuration file

config ARCH_alpha

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_USE_MMU

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    help

      The Alpha architecture.