timer: gxp: Add HPE GXP timer support

Add support for the HPE GXP SOC timer. The GXP supports several different
kinds of timers but for the purpose of this driver there is only support
for the General Timer. The timer has a 1us resolution and is 56 bits.

Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>
diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index 7b8ab56..d592dba 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -139,6 +139,13 @@
 	  Enables support for the Designware APB Timer driver. This timer is
 	  present on Altera SoCFPGA SoCs.
 
+config GXP_TIMER
+	bool "HPE GXP Timer"
+	depends on TIMER
+	help
+	  Enables support for the GXP Timer driver. This timer is
+	  present on HPE GXP SoCs.
+
 config MPC83XX_TIMER
 	bool "MPC83xx timer support"
 	depends on TIMER