[U-Boot] at91 gpio: fix typo in compatibility macro

[Andreas Bießmann]

Dear Andreas Henriksson,

Andreas Henriksson <andreas.henriksson at endian.se> writes:
>It's called _pio_ in the version that was added to git.
>Apparently it got renamed without updating the macros before it was
>applied, c.f.
>http://u-boot.10912.n7.nabble.com/U-Boot-PATCH-3-9-V3-add-a-new-AT91-GPIO-driver-td75922.html
>
>Signed-off-by: Andreas Henriksson <andreas.henriksson at endian.se>
>
>---
>arch/arm/include/asm/arch-at91/gpio.h |    2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)

applied to u-boot-atmel/master, thanks!

Best regards,
Andreas Bießmann