drivers: i2c: Kconfig.stm32: enable combined interrupt for STM32MP2

According to the STM32MP2 reference manual, the I2C controller uses
a single interrupt line for all events (EV + ERR), so the combined
interrupt must be enabled for the STM32MP2 series.

Signed-off-by: Tanguy Raufflet <tanguy.raufflet@savoirfairelinux.com>