cppcheck cleanup: fix nullPointer errors

There are a number of places where U-Boot intentionally and legally
accesses physical address 0x0000, for example when installing
exception vectors on systems where these are located in low memory.

Add "cppcheck-suppress nullPointer" comments to silence cppcheck
where this is intentional and legal.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/arch/arm/cpu/arm926ejs/mxs/mxs.c b/arch/arm/cpu/arm926ejs/mxs/mxs.c
index 365542f..ef130ae 100644
--- a/arch/arm/cpu/arm926ejs/mxs/mxs.c
+++ b/arch/arm/cpu/arm926ejs/mxs/mxs.c
@@ -83,7 +83,9 @@
 	int i;
 
 	for (i = 0; i < 8; i++) {
+		/* cppcheck-suppress nullPointer */
 		vt[i] = ldr_pc;
+		/* cppcheck-suppress nullPointer */
 		vt[i + 8] = start_addr + (4 * i);
 	}
 }
diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c
index d3e1369..d29b9aa 100644
--- a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c
+++ b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c
@@ -118,6 +118,8 @@
 	 * fine.
 	 */
 	extern uint32_t _start;
+
+	/* cppcheck-suppress nullPointer */
 	memcpy(0x0, &_start, 0x60);
 }
 
diff --git a/arch/arm/cpu/armv7/zynq/ddrc.c b/arch/arm/cpu/armv7/zynq/ddrc.c
index 1ea086d..d74f8db 100644
--- a/arch/arm/cpu/armv7/zynq/ddrc.c
+++ b/arch/arm/cpu/armv7/zynq/ddrc.c
@@ -40,6 +40,7 @@
 		 * first stage bootloader. To get ECC to work all memory has
 		 * been initialized by writing any value.
 		 */
+		/* cppcheck-suppress nullPointer */
 		memset((void *)0, 0, 1 * 1024 * 1024);
 	} else {
 		puts("ECC disabled ");