python-numpy: reformat BR2_PACKAGE_PYTHON_NUMPY_ARCH_SUPPORTS

Current BR2_PACKAGE_PYTHON_NUMPY_ARCH_SUPPORTS variable layout going
to be inconvenient and ugly for adding new architectures or
restricting specific architectures. Lets reformat layout of this
variable.

Signed-off-by: Evgeniy Didin <didin@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: arc-buildroot@synopsys.com
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>