Making si_swapinfo exportable

If we will make si_swapinfo() exportable it could be called from modules.
Otherwise modules have no interface to obtain information about swap usage.
Change made in the same way as si_meminfo() declared.

Signed-off-by: Leonid Moiseichuk <leonid.moiseichuk@nokia.com>
arm: tenderloin: use more memory for GPU rendering

Signed-off-by: Simon Busch <morphis@gravedo.de>