driver: eSPI: npcx: workaround the errata rev1_2, No.3.10

Enabling an eSPI channel (r.g. Peripheral Channel, Virtual Wire Channel,
etc.) during an eSPI transaction might (with low probability) cause the
eSPI_SIF module to transition to a wrong state and therefore response
with FATAL_ERROR on an incoming transaction.
This CL workarounds this issue by clearing the bit 4 of NPCX eSPI
specific register#2.

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>