arm64: head: fix code comments in set_cpu_boot_mode_flag

Up to here, the CPU boot mode can either be EL1 or EL2.
Correct the code comments a bit.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210518101405.1048860-5-aisheng.dong@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: Dong Aisheng

arch/arm64/kernel/head.S

@@ -550,7 +550,7 @@ SYM_FUNC_START_LOCAL(set_cpu_boot_mode_flag)
 	cmp	w0, #BOOT_CPU_MODE_EL2
 	b.ne	1f
 	add	x1, x1, #4
-1:	str	w0, [x1]			// This CPU has booted in EL1
+1:	str	w0, [x1]			// Save CPU boot mode
 	dmb	sy
 	dc	ivac, x1			// Invalidate potentially stale cache line
 	ret