android: enable swrast w/o radeonsi build

android: enable swrast w/o radeonsi build

There has been a cross dependency between swrast and radeonsi builds,
as gallium/auxiliary requires that libLLVM provides the symbols in
libLLVMExecutionEngine, libLLVMRuntimeDyld and libLLVMMCJIT

In order to avoid having to enable radeonsi to properly build swast,
libLLVMExecutionEngine, libLLVMRuntimeDyld and libLLVMMCJIT
are added to device libLLVM as whole static dependecies.

For simplification these common dependencies are set as unconditional
and llvm_device_static_libraries is used to keep existing code style.

libAMDGPU* dependencies are now defined as strictly radeonsi conditional.