Blackfin arch: fix bug - traps test case 19 for exception 0x2d fails

Enable null pointer checking for ICPLBs. The code was there but for
some reason I had commented it out at some stage during development.

Should restrict this to 1K since atomic ops start there.
Signed-off-by: NBernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: NBryan Wu <cooloney@kernel.org>

arch/blackfin/kernel/cplb-mpu/cplbinit.c

@@ -63,10 +63,8 @@ void __init generate_cplb_tables_cpu(unsigned int cpu)
 	dcplb_tbl[cpu][i_d].addr = 0;
 	dcplb_tbl[cpu][i_d++].data = SDRAM_OOPS | PAGE_SIZE_1KB;
 
-#if 0
 	icplb_tbl[cpu][i_i].addr = 0;
-	icplb_tbl[cpu][i_i++].data = i_cache | CPLB_USER_RD | PAGE_SIZE_4KB;
-#endif
+	icplb_tbl[cpu][i_i++].data = i_cache | CPLB_USER_RD | PAGE_SIZE_1KB;
 
 	/* Cover kernel memory with 4M pages.  */
 	addr = 0;