reiserfs: remove workaround code for GCC 3.x

reiserfs: remove workaround code for GCC 3.x

cafa0010cd51 ("Raise the minimum required gcc version to 4.6") bumped the
minimum GCC version to 4.6 for all architectures.

The workaround code in fs/reiserfs/Makefile is obsolete now.

Link: http://lkml.kernel.org/r/1535337230-13222-1-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>