ARM: shmobile: Remove obsolete sh-gpio.h

The last user of "sh-gpio.h" was removed in commit 1fa59bda


("ARM: shmobile: Remove legacy board code for Armadillo-800 EVA").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>