There is off-by-one error in sandbox_emul_gpio that causes
segfault of certain tests.
EMUL_GPIO_REG_END is the address of last valid (emulated) register.
This patch fixed this (by adding one more element to emulated register array).
Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Tested-by: Stephen Warren <swarren@nvidia.com>