mimxrt/mpconfigport: Enable support for exFAT.

There is plenty of room in the MIMXRT board flash, so it can be enabled.

Tested with:
- MIMXRT1176_EVK
- MIMXRT1061 (Teensy 4.1)
- MIMXRT1010 (Olimex RT1010)

Signed-off-by: robert-hh <robert@hammelrath.com>

Author: robert-hh

ports/mimxrt/mpconfigport.h

@@ -125,6 +125,7 @@ uint32_t trng_random_u32(void);
 #define MICROPY_FATFS_RPATH                 (2)
 #define MICROPY_FATFS_MULTI_PARTITION       (1)
 #define MICROPY_FATFS_MAX_SS                (4096)
+#define MICROPY_FATFS_EXFAT                 (1)
 
 #ifndef MICROPY_PY_NETWORK
 #define MICROPY_PY_NETWORK                  (1)