Handle interrupt acknowledge register in Cortex-A53 SRE port (#392)

Let the FreeRTOS IRQ handler properly store and restore the ICCIAR
register value around the vApplicationIRQHandler() call.

Signed-off-by: Stephane Viau <stephane.viau@oss.nxp.com>

Co-authored-by: Stephane Viau <stephane.viau@oss.nxp.com>
Co-authored-by: Gaurav-Aggarwal-AWS <33462878+aggarg@users.noreply.github.com>

portable/GCC/ARM_CA53_64_BIT_SRE/portASM.S

@@ -303,6 +303,13 @@ FreeRTOS_IRQ_Handler:
 	/* Maintain the interrupt nesting information across the function call. */
 	STP		X1, X5, [SP, #-0x10]!
 
+	/* Read value from the interrupt acknowledge register, which is stored in W0
+	for future parameter and interrupt clearing use. */
+	MRS		X0, S3_0_C12_C12_0 /* read ICC_IAR1_EL1 and store ICCIAR in X0 as parameter */
+
+	/* Maintain the ICCIAR value across the function call. */
+	STP		X0, X1, [SP, #-0x10]!
+
 	/* Call the C handler. */
 	BL vApplicationIRQHandler
 
@@ -311,6 +318,12 @@ FreeRTOS_IRQ_Handler:
 	DSB		SY
 	ISB		SY
 
+	/* Restore the ICCIAR value. */
+	LDP		X0, X1, [SP], #0x10
+
+	/* End IRQ processing by writing ICCIAR to the EOI register. */
+	MSR		S3_0_C12_C12_1, X0	/* ICC_EOIR1_EL1 */
+
 	/* Restore the critical nesting count. */
 	LDP		X1, X5, [SP], #0x10
 	STR		X1, [X5]