For varying privacy and security reasons, sometimes we would like to
completely silence the _serial_ console, and only enable it when needed.

But there are many existing systems that depend on this _serial_ console,
so add acpi=nospcr to disable console in ACPI SPCR table as default
_serial_ console.
Signed-off-by: Liu Wei <liuwei09@cestc.cn>
Suggested-by: Prarit Bhargava <prarit@redhat.com>
Suggested-by: Will Deacon <will@kernel.org>
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Link: https://lore.kernel.org/r/20240625030504.58025-1-liuwei09@cestc.cnSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>