perf: arm_spe: Drop BIT() and use FIELD_GET/PREP accessors

perf: arm_spe: Drop BIT() and use FIELD_GET/PREP accessors

Now that generated sysregs are in place, update the register field
accesses. The use of BIT() is no longer needed with the new defines. Use
FIELD_GET and FIELD_PREP instead of open coding masking and shifting.

No functional change.

Tested-by: James Clark <james.clark@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220825-arm-spe-v8-7-v4-4-327f860daf28@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>