arm64: entry: Remove confusing comment

The comment about SYS_MEMBARRIER_SYNC_CORE relying on ERET being
context-synchronizing is confusing and misplaced with kpti. Given that
this is already documented under Documentation/ (see arch-support.txt
for membarrier), remove the comment altogether.
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/entry.S

@@ -344,10 +344,6 @@ alternative_else_nop_endif
 	ldp	x28, x29, [sp, #16 * 14]
 	ldr	lr, [sp, #S_LR]
 	add	sp, sp, #S_FRAME_SIZE		// restore sp
-	/*
-	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
-	 * when returning from IPI handler, and when returning to user-space.
-	 */
 
 	.if	\el == 0
 alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0