ARM: at91: delete the pcontrol_g20_defconfig

ARM: at91: delete the pcontrol_g20_defconfig

In routine testing I found this file should not specify a site
specific toolchain path.  I suggested that the defconfigs should
not be calling out site specific toolchain locations, so we should
delete the setting of CROSS_COMPILE.  In response, it was indicated
that this is an obsolete defconfig and it should simply be deleted.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>