[Buildroot] how to tune powerpc e500v2 cpus in BR

[raymond zhao]

Hi,
I am using freescale's p1020 CPU. It is a e500v2 core. How could I
config the build root to tune the tool chain for the following
options:

-mcpu=8548 -mspe=yes -mabi=spe -mhard-float -mfloat-gprs=double

>From the menuconfig, I can only select CPU as 8540.

Thanks,

Raymond