devices: legacy: Add Arm PL061 GPIO controller

This commit implements ARM PrimeCell General Purpose Input/Output
(GPIO) PL061 device specification.

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
Signed-off-by: Henry Wang <Henry.Wang@arm.com>

devices/src/legacy/mod.rs

@@ -9,6 +9,8 @@
 mod cmos;
 #[cfg(feature = "fwdebug")]
 mod fwdebug;
+#[cfg(target_arch = "aarch64")]
+mod gpio_pl061;
 mod i8042;
 #[cfg(target_arch = "aarch64")]
 mod rtc_pl031;