powerpc/prom_init: drop PROM_BUG()

Unused, let's drop it.
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220920122302.99195-3-david@redhat.com

arch/powerpc/kernel/prom_init.c

@@ -96,12 +96,6 @@ static int of_workarounds __prombss;
 #define OF_WA_CLAIM	1	/* do phys/virt claim separately, then map */
 #define OF_WA_LONGTRAIL	2	/* work around longtrail bugs */
 
-#define PROM_BUG() do {						\
-        prom_printf("kernel BUG at %s line 0x%x!\n",		\
-		    __FILE__, __LINE__);			\
-	__builtin_trap();					\
-} while (0)
-
 #ifdef DEBUG_PROM
 #define prom_debug(x...)	prom_printf(x)
 #else