[oe] spca5xx does not build

[Holger Freyther]

> | make[1]: Entering directory
> `/home/vdubhack/overo-oe/tmp/sysroots/overo-angstrom-linux-gnueabi/kernel'
> | scripts/Makefile.build:49: *** CFLAGS was changed in
> "/home/vdubhack/overo-oe/tmp/work/overo-angstrom-linux-gnueabi/spca5xx-20060501-r81/spca5xx-20060501/Makefile".
> Fix it to use EXTRA_CFLAGS.  Stop.
>