linux/export: clean up the IA-64 KSYM_FUNC macro

With commit cf8e8658

 ("arch: Remove Itanium (IA-64) architecture"),
there is no need to keep the IA-64 definition of the KSYM_FUNC macro.

Clean up the IA-64 definition of the KSYM_FUNC macro.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>