Trivial: Style fix

make the style checker happy

seL4_libs: remove autoconf.h from seL4_libs

this commit removes autoconf.h generation from each lib and
append '#include <<lib_name>/gen_config.h>' after each
'#include <autoconf.h>' since autoconf.h is only the for the
kernel config now. This is a temporarily solution, since we
currently don't have a way to tell which header files each file
is trying to include when it includes 'autoconf.h'

SELFOUR-1239: riscv: merge arch and sel4_arch/arch.c

- riscv doesn't need sel4_arch, remove it
- merge arch.c
- add src/arch to build files

riscv: fix licenses

NICTA_BSD -> DATA61_BSD

RISC-V port