drivers: st: move i2c driver in its own folder

The driver could be used for other devices than PMIC.

Change-Id: I4569e7c0028e52e1ff2fe9d38f11de11e95d1897
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/plat/st/stm32mp1/platform.mk b/plat/st/stm32mp1/platform.mk
index 60852c6..e9a6af2 100644
--- a/plat/st/stm32mp1/platform.mk
+++ b/plat/st/stm32mp1/platform.mk
@@ -51,7 +51,7 @@
 				drivers/st/clk/stm32mp1_clkfunc.c			\
 				drivers/st/ddr/stm32mp1_ddr_helpers.c			\
 				drivers/st/gpio/stm32_gpio.c				\
-				drivers/st/pmic/stm32_i2c.c				\
+				drivers/st/i2c/stm32_i2c.c				\
 				drivers/st/pmic/stm32mp1_pmic.c				\
 				drivers/st/pmic/stpmu1.c				\
 				drivers/st/reset/stm32mp1_reset.c			\