cfi: fix more -Wformat warnings

cfi: fix more -Wformat warnings

Building cfi with recent clang on a 64-bit system results in the
following warnings:

    compiler-rt/lib/cfi/cfi.cpp:233:64: warning: format specifies type 'void *' but the argument has type '__sanitizer::uptr' (aka 'unsigned long') [-Wformat]
        VReport(1, "Can not handle: symtab > strtab (%p > %zx)\n", symtab, strtab);
                                                     ~~            ^~~~~~
                                                     %lu
    compiler-rt/lib/sanitizer_common/sanitizer_common.h:231:46: note: expanded from macro 'VReport'
        if ((uptr)Verbosity() >= (level)) Report(__VA_ARGS__); \
                                                 ^~~~~~~~~~~
    compiler-rt/lib/cfi/cfi.cpp:253:59: warning: format specifies type 'void *' but the argument has type '__sanitizer::uptr' (aka 'unsigned long') [-Wformat]
        VReport(1, "Can not handle: symtab %p, strtab %zx\n", symtab, strtab);
                                           ~~                 ^~~~~~
                                           %lu
    compiler-rt/lib/sanitizer_common/sanitizer_common.h:231:46: note: expanded from macro 'VReport'
        if ((uptr)Verbosity() >= (level)) Report(__VA_ARGS__); \
                                                 ^~~~~~~~~~~

Since `__sanitizer::uptr` has the same size as `size_t`, consistently
use `%z` as a printf specifier.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D114466