UPSTREAM: arm64: kernel: Add min_field_value and use '>=' for feature detection

When a new cpu feature is available, the cpu feature bits will have some
initial value, which is incremented when the feature is updated.
This patch changes 'register_value' to be 'min_field_value', and checks
the feature bits value (interpreted as a signed int) is greater than this
minimum.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Bug: 31432001
Change-Id: Iac5f107779f27e214eaa42f7d24467e27d1c6774
(cherry picked from commit 18ffa046c509d0cd011eeea2c0418f2d014771fc)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>