[openocd] Enable sysfsgpio support

[drws]

OpenOCD's PKGBUILD* is missing build flags to enable support for generic GPIOs - sysfsgpio:

[url]https://www.openocd.org/doc/doxygen/html/sysfsgpio_8c.html[/url]

The flag "sysfsgpio" has to be added to "_features". The package with added features builds on a Raspberry Pi (armv7h).

While at it, the PKGBUILD is also missing correct ARM architectures:

[code]arch=('armv7h' 'aarch64')[/code]

* [url]https://archlinuxarm.org/packages/armv7h/openocd/files/PKGBUILD[/url]