mfd: dm355evm_msp: Fix checkpatch error: insert space after ','

This is part of an effort to clean-up the MFD subsystem.

ERROR: space required after that ',' (ctx:VxV)
+#define MSP_GPIO(bit,reg)      ((DM355EVM_MSP_ ## reg) << 3 | (bit))
                     ^

total: 1 errors, 0 warnings, 437 lines checked

Signed-off-by: Lee Jones <lee.jones@linaro.org>