cc/gcc: remove 'sub-level' version form symbols

Now we use defconfig files to store the samples, we have to be a bit more
conservatives in the symbols names, so as to avoid gigantic version bumps
when updating sub-level versions from a package.

For example (using fictitious versions):
- in crosstool-NG 1.17.0, we choose:
- latest gcc is gcc-linaro-4.7-2012.10, which is the default for the
choice in the menuconfig
- gcc-linaro-4.6-2012.10 is selected
- so, sample has an explicit symbol for the selected gcc version, as it
is not the default
- we update to crosstool-NG 1.18.0:
- latest gcc version is gcc-linaro-4.7-2013.01
- gcc-linaro-46 has been updated to gcc-linaro-4.6-2013.01
- as the sample now has no *valid* symbol to set the gcc version, the
default is used, while we would have expected to still use the 4.6
release from linaro, not the 4.7

Get rid of sub-level (ie. the third digit sequence in versions) from the
symbols for linaro versions.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # MIPS specific config options

 choice

     bool

     prompt "ABI"

 config ARCH_mips_o32

     bool

     prompt "o32"

     depends on ARCH_32

     help

       This is the -mabi=32 gcc option.

 config ARCH_mips_n32

     bool

     prompt "n32"

     depends on ARCH_64

     help

       This is the -mabi=n32 gcc option.

 config ARCH_mips_n64

     bool

     prompt "n64"

     depends on ARCH_64

     help

       This is the -mabi=64 gcc option.

 # Not supported on Linux:

 # o64   : seems related to *BSD

 # eabi  : seems related to bare-metal

 endchoice

 config ARCH_mips_ABI

     string

     default "32"    if ARCH_mips_o32

     default "n32"   if ARCH_mips_n32

     default "64"    if ARCH_mips_n64