microblaze: Do not use _start in vmlinux

_start symbol stores physical address where kernel is.
Gdb uses this symbol for their purpose that's why
we have to rename it.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/boot/Makefile

@@ -35,7 +35,7 @@ quiet_cmd_cp = CP      $< $@$2
 	cmd_cp = cat $< >$@$2 || (rm -f $@ && echo false)
 
 quiet_cmd_strip = STRIP   $@
-	cmd_strip = $(STRIP) -K _start -K _end -K __log_buf \
+	cmd_strip = $(STRIP) -K microblaze_start -K _end -K __log_buf \
 				-K _fdt_start vmlinux -o $@
 
 quiet_cmd_uimage = UIMAGE  $@.ub

arch/microblaze/kernel/vmlinux.lds.S

@@ -10,7 +10,7 @@
 
 OUTPUT_FORMAT("elf32-microblaze", "elf32-microblaze", "elf32-microblaze")
 OUTPUT_ARCH(microblaze)
-ENTRY(_start)
+ENTRY(microblaze_start)
 
 #include <asm/page.h>
 #include <asm-generic/vmlinux.lds.h>
@@ -20,7 +20,7 @@ jiffies = jiffies_64 + 4;
 
 SECTIONS {
 	. = CONFIG_KERNEL_START;
-	_start = CONFIG_KERNEL_BASE_ADDR;
+	microblaze_start = CONFIG_KERNEL_BASE_ADDR;
 	.text : AT(ADDR(.text) - LOAD_OFFSET) {
 		_text = . ;
 		_stext = . ;