arch/arm/src/stm32/hardware/stm32_exti.h:
* Change STM32_EXTI2_OFFSET (offset to EXTI2 registers) from 0x18
to 0x20. This symbol is defined when CONFIG_STM32_STM32F30XX or
CONFIG_STM32_STM32F33XX. According to the current reference
manuals for STM32F334xx (RM0364 rev 4) and STM32F302xx (RM0365
rev 8), EXTI_IMR1 is at offset 0x00 and EXTI_IMR2 is at offset
0x20, i.e., 0x20 apart. The same offset applies to the rest of
the registers: EMR1/EMR2, RTSR1/RTSR2, etc.