x86: Rename __{start,end}_init_task to __{start,end}_init_stack

The stack of a task has been separated from the memory of a task_struct
struture for a long time on x86, as a result __{start,end}_init_task no
longer mark the start and end of the init_task structure, but its stack
only.

Rename __{start,end}_init_task to __{start,end}_init_stack.

Note other architectures are not affected because __{start,end}_init_task
are used on x86 only.
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20240322081616.3346181-1-xin@zytor.com

arch/x86/kernel/vmlinux.lds.S

@@ -173,7 +173,7 @@ SECTIONS
 		INIT_TASK_DATA(THREAD_SIZE)
 
 		/* equivalent to task_pt_regs(&init_task) */
-		__top_init_kernel_stack = __end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE;
+		__top_init_kernel_stack = __end_init_stack - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE;
 
 #ifdef CONFIG_X86_32
 		/* 32 bit has nosave before _edata */

include/asm-generic/vmlinux.lds.h

@@ -399,13 +399,13 @@
 
 #define INIT_TASK_DATA(align)						\
 	. = ALIGN(align);						\
-	__start_init_task = .;						\
+	__start_init_stack = .;						\
 	init_thread_union = .;						\
 	init_stack = .;							\
 	KEEP(*(.data..init_task))					\
 	KEEP(*(.data..init_thread_info))				\
-	. = __start_init_task + THREAD_SIZE;				\
-	__end_init_task = .;
+	. = __start_init_stack + THREAD_SIZE;				\
+	__end_init_stack = .;
 
 #define JUMP_TABLE_DATA							\
 	. = ALIGN(8);							\