driver: i2c: npcx: adjust parameters for better I2C timing at 100 KHz

The original parameter (k1) setting may let the I2C frequency be a
little bit higher than 100k Hz, which causes the timing Tsu:sta (set-up
time for a repeated START) to violate the spec. This change fixes the k1
parameter and also changes the HLDT to the suggested value in the
datasheet.

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