arch/sparc: add absic support

Add support for building SPARC targeted toolchain.
With this patch I have built a working sparc V8 (32 toolchain).

Testing shows that not all gcc versions works well:
4.4.1 OK (kernel builds and the final kernel can boot)
4.4.2 Not tested
4.4.3 Not tested
4.4.4 BAD (Kernel can build but fails during boot)
4.4.5 BAD (Kernel can build but fails during boot)
4.5.1 BAD (Build fails with a spill related ICE - http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35664)
4.5.2 OK (kernel builds and boots)

I have successfully been using the 4.5.2 version for a few months.

This patch does not add support for the LEON variant.
That may come later.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[yann.morin.1998@anciens.enib.fr: for 32-bit, default CT_TARGET_ARCH is OK]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 # Super-H specific configuration file

 choice

     bool

     prompt "Variant"

 config ARCH_SH_SH3

     bool

     prompt "sh3"

 config ARCH_SH_SH4

     bool

     prompt "sh4"

 config ARCH_SH_SH4A

     bool

     prompt "sh4a"

 endchoice

 config ARCH_SH_VARIANT

     string

     default "sh3"   if ARCH_SH_SH3

     default "sh4"   if ARCH_SH_SH4

     default "sh4a"  if ARCH_SH_SH4A