[hwasan] Fix -Wunneeded-internal-declaration by declaring static inline

https://reviews.llvm.org/D149386 caused a buildbot error (https://lab.llvm.org/buildbot#builders/37/builds/21766):

'In file included from /b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/hwasan/hwasan_interceptors.cpp:18:
/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/hwasan/hwasan_checks.h:128:53: error: 'static' function 'PossiblyShortTagMatches' declared in header file should be declared 'static inline' [-Werror,-Wunneeded-internal-declaration]
__attribute__((always_inline, nodebug)) static bool PossiblyShortTagMatches('

This patch simply adds the inline annotation.

Differential Revision: https://reviews.llvm.org/D149402