tools/gpio: add install section

Allow user to call install target.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/tools/Makefile b/tools/Makefile
index f10b64d8..daa8fb3 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -85,7 +85,7 @@
 freefall: FORCE
 	$(call descend,laptop/$@)
 
-all: acpi cgroup cpupower hv firewire lguest \
+all: acpi cgroup cpupower gpio hv firewire lguest \
 		perf selftests turbostat usb \
 		virtio vm net x86_energy_perf_policy \
 		tmon freefall objtool
@@ -96,7 +96,7 @@
 cpupower_install:
 	$(call descend,power/$(@:_install=),install)
 
-cgroup_install firewire_install hv_install lguest_install perf_install usb_install virtio_install vm_install net_install objtool_install:
+cgroup_install firewire_install gpio_install hv_install lguest_install perf_install usb_install virtio_install vm_install net_install objtool_install:
 	$(call descend,$(@:_install=),install)
 
 selftests_install:
@@ -114,7 +114,8 @@
 kvm_stat_install:
 	$(call descend,kvm/$(@:_install=),install)
 
-install: acpi_install cgroup_install cpupower_install hv_install firewire_install lguest_install \
+install: acpi_install cgroup_install cpupower_install gpio_install \
+		hv_install firewire_install lguest_install \
 		perf_install selftests_install turbostat_install usb_install \
 		virtio_install vm_install net_install x86_energy_perf_policy_install \
 		tmon_install freefall_install objtool_install kvm_stat_install