arm64: arch_timer: document Hisilicon erratum 161010101

Now that we have a workaround for Hisilicon erratum 161010101, notes
this in the arm64 silicon-errata document.

The new config option is too long to fit in the existing kconfig column,
so this is widened to accomodate it. At the same time, an existing
whitespace error is corrected, and the existing pattern of a line space
between vendors is enforced for recent additions.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
[Mark: split patch, reword commit message, rework table]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>