trezorhal: use static inline instead of static (gcc 7.2 workaround)

embed/trezorhal/flash.h

@@ -51,7 +51,7 @@ secbool flash_lock(void);
 const void *flash_get_address(uint8_t sector, uint32_t offset, uint32_t size);
 
 secbool flash_erase_sectors(const uint8_t *sectors, int len, void (*progress)(int pos, int len));
-inline secbool flash_erase_sector(uint8_t sector) { return flash_erase_sectors(&sector, 1, NULL); }
+static inline secbool flash_erase_sector(uint8_t sector) { return flash_erase_sectors(&sector, 1, NULL); }
 secbool flash_write_byte(uint32_t address, uint8_t data);
 secbool flash_write_word(uint32_t address, uint32_t data);
 secbool flash_write_byte_rel(uint8_t sector, uint32_t offset, uint8_t data);