coresight-tpdm: Add support to enable the lane for MCMB TPDM

Add the sysfs file to set/get the enablement of the lane. For MCMB
configurations, the field "E_LN" in CMB_CR register is the
individual lane enables. MCMB lane N is enabled for trace
generation when M_CMB_CR.E=1 and M_CMB_CR.E_LN[N]=1. For lanes
that are not implemented on a given MCMB configuration, the
corresponding bits of this field read as 0 and ignore writes.

Signed-off-by: Tao Zhang <quic_taozha@quicinc.com>
Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250226064008.2531037-4-quic_jinlmao@quicinc.com