arm64: mm: Remove unused declaration early_io_map()

Commit bf4b558e ("arm64: add early_ioremap support") removed the
implementation but leave declaration.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240805140038.1366033-1-yuehaibing@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>