dm: Add Hardware Spinlock class

This is uclass for Hardware Spinlocks.
It implements two mandatory operations: lock and unlock
and one optional relax operation.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/drivers/Makefile b/drivers/Makefile
index 55de109..c425831 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -113,4 +113,5 @@
 obj-$(CONFIG_W1_EEPROM) += w1-eeprom/
 
 obj-$(CONFIG_MACH_PIC32) += ddr/microchip/
+obj-$(CONFIG_DM_HWSPINLOCK) += hwspinlock/
 endif