stm32f0: Fix EC slave I2C interrupt
stm32f0: Fix EC slave I2C interrupt

The interrupt handler is hardcoded to I2C1. We should choose between
I2C1 and I2C2 based on I2C_PORT_EC.

BUG=chrome-os-partner:30707
TEST=On Ryu, ectool hello and see ACK.
BRANCH=None

Change-Id: I07055b0ee7459e6cac5585737e200ff2d5814a34
Signed-off-by: Vic Yang <5fd92abeee651458f98e2856f4f200ee971cee4d@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/209960
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

longsleep/ec,thehobn/ec,eatbyte/chromium-ec,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec,md5555/ec,coreboot/chrome-ec,coreboot/chrome-ec,longsleep/ec,fourier49/BZ_DEV_EC,thehobn/ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,fourier49/BIZ_EC,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,coreboot/chrome-ec,md5555/ec,coreboot/chrome-ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,eatbyte/chromium-ec,fourier49/BIZ_EC,thehobn/ec,thehobn/ec,mtk09422/chromiumos-platform-ec,fourier49/BZ_DEV_EC,mtk09422/chromiumos-platform-ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,eatbyte/chromium-ec,longsleep/ec