i2c: npcm: Fix timeout calculation

Use adap.timeout for timeout calculation instead of hard-coded
value of 35ms.

Fixes: 56a1485b ("i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver")
Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>