I2C: mv_i2c: fix build issue when enable debug option

When DEBUG_I2C is open, the following build issue would shows up.

mv_i2c.c: In function 'i2c_transfer':
mv_i2c.c:257: error: 'ISR' undeclared (first use in this function)
mv_i2c.c:257: error: (Each undeclared identifier is reported only once
mv_i2c.c:257: error: for each function it appears in.)

Signed-off-by: Lei Wen <leiwen@marvell.com>

drivers/i2c/mv_i2c.c

@@ -253,7 +253,7 @@ transfer_error_bus_busy:
 		ret = -6; goto i2c_transfer_finish;
 
 i2c_transfer_finish:
-		PRINTD(("i2c_transfer: ISR: 0x%04x\n", ISR));
+		PRINTD(("i2c_transfer: ISR: 0x%04x\n", readl(&base->isr)));
 		i2c_reset();
 		return ret;
 }