stm32mp1: Add remoteproc support for m4 coprocessor

Alignment with kernel patch proposal for binding:

[PATCH v4 0/8] stm32 m4 remoteproc on STM32MP157c
https://lkml.org/lkml/2019/5/14/159

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/stm32mp15_optee_defconfig b/configs/stm32mp15_optee_defconfig
index e5b9be7..177cbc7 100644
--- a/configs/stm32mp15_optee_defconfig
+++ b/configs/stm32mp15_optee_defconfig
@@ -23,6 +23,7 @@
 CONFIG_CMD_GPT=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
+CONFIG_CMD_REMOTEPROC=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_SPI=y
 CONFIG_CMD_USB=y