s390: fix unrecognized __aligned() in uapi header

s390: fix unrecognized __aligned() in uapi header

__aligned() is a shorthand that is only available in the kernel space
because it is defined in include/linux/compiler_attributes.h, which is
not exported to the user space.

Detected by compile-testing exported headers.

./usr/include/asm/runtime_instr.h:60:37: error: expected declaration specifiers or ‘...’ before numeric constant
 } __attribute__((packed)) __aligned(8);
                                     ^

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>