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>

arch/blackfin/cpu/initcode.c

@@ -955,6 +955,7 @@ check_hibernation(ADI_BOOT_DATA *bs, u16 vr_ctl, bool put_into_srfs)
 		uint32_t *hibernate_magic = 0;
 
 		SSYNC();
+		/* cppcheck-suppress nullPointer */
 		if (hibernate_magic[0] == 0xDEADBEEF) {
 			serial_putc('c');
 			bfin_write_EVT15(hibernate_magic[1]);