driver: eSPI: npcx: support multiple bytes mode for Port80

eSPI PUT_IOWR_SHORT protocol can send 1/2/4 bytes of data in a single
transaction. This allows the host to send max 32-bits Port80 code
at one time. This CL sets bits OFS0_SEL~OFS3_SEL in the DPAR1 register
to let the EC hardware put the full Port80 code to DP80BUF FIFO.
It also groups the N-byte code into a single 32-bits variable when
necessary by analyzing the offset field in the DP80BUF register.

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