feat(imx8ulp): allow RTD to reset APD through MU

Clear HRM bit in MU0_B CCR0 register to allow RTD to reset APD.
The action needs at both ATF init and APD resume.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: I2475e34b13f57818580a478ab567bfb9fc6cf174
diff --git a/plat/imx/imx8ulp/apd_context.c b/plat/imx/imx8ulp/apd_context.c
index dad3d77..8f179e7 100644
--- a/plat/imx/imx8ulp/apd_context.c
+++ b/plat/imx/imx8ulp/apd_context.c
@@ -561,6 +561,8 @@
 	/* FIXME: make uart work for ATF */
 	mmio_write_32(IMX_LPUART_BASE + 0x18, 0xc0000);
 
+	/* Allow M core to reset A core */
+	mmio_clrbits_32(IMX_MU0B_BASE + 0x10, BIT(2));
 	/*
 	 * Ask S400 to release caam to APD as it is owned by s400
 	 */