libpayload: Fix the stack and data labels

We should make sure _stack/_estack and the other labels are consistent.
And _data & _edata is also useful to clean up the sensitive data on the
data section.

BUG=b:248610274
TEST=emerge-cherry libpayload
BRANCH=none

Cq-Depend: chromium:5052462
Change-Id: I589040f4db60b35813ea9f4ba9503244bd7def00
Signed-off-by: Yi Chou <yich@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79144
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

payloads/libpayload/arch/arm/libpayload.ldscript

@@ -40,29 +40,35 @@ SECTIONS
 	_start = .;
 
 	.text : {
+		_text = .;
 		*(.text._entry)
 		*(.text)
 		*(.text.*)
+		_etext = .;
 	}
 
 	.rodata : {
+		_rodata = .;
 		*(.rodata)
 		*(.rodata.*)
+		_erodata = .;
 	}
 
 	.data : {
+		_data = .;
 		*(.data)
 		*(.data.*)
+		_edata = .;
 	}
 
-	_edata = .;
-
 	.bss : {
+		_bss = .;
 		*(.sbss)
 		*(.sbss.*)
 		*(.bss)
 		*(.bss.*)
 		*(COMMON)
+		_ebss = .;
 
 		/* Stack and heap */
 
@@ -72,10 +78,10 @@ SECTIONS
 		. = ALIGN(16);
 		_eheap = .;
 
-		_estack = .;
+		_stack = .;
 		. += CONFIG_LP_STACK_SIZE;
 		. = ALIGN(16);
-		_stack = .;
+		_estack = .;
 	}
 
 	_end = .;