objtool: Remove workaround for unreachable warnings from old GCC

objtool: Remove workaround for unreachable warnings from old GCC

Commit 46ed35d9f3fa ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.

This effectively reverts commit 2ee428c74ebb ("objtool: Skip unreachable
warnings for GCC 4.4 and older"), which was a workaround for GCC 4.4 or
older.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-kbuild@vger.kernel.org
Link: https://lkml.kernel.org/r/1535341183-19994-1-git-send-email-yamada.masahiro@socionext.com