radix tree test suite: Fix compilation

Commit 4bba4c4b added tools/include/linux/compiler_types.h which
includes linux/compiler-gcc.h.  Unfortunately, we had our own (empty)
compiler_types.h which overrode the one added by that commit, and
so we lost the definition of __must_be_array().  Removing our empty
compiler_types.h fixes the problem and reduces our divergence from the
rest of the tools.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>