include/asm-generic/vmlinux.lds.h: make readmostly section correctly align

The readmostly section should end at a cacheline aligned address,
otherwise the last several data might share cachline with other data and
make the readmostly data still have cache bounce.

For example, in ia64, secpath_cachep is the last readmostly data, and it
shares cacheline with init_uts_ns.

a000000100e80480 d secpath_cachep
a000000100e80488 D init_uts_ns

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>