[C61][SPL][uSD] Fix the management of uSD CD pin in the SPL
Use the proper SD2_CD_B pin as Chip Detect (CD) for usdhc2 Up to now SD2_DATA3 was used to do it but sometimes it doesn't work
Use the proper SD2_CD_B pin as Chip Detect (CD) for usdhc2 Up to now SD2_DATA3 was used to do it but sometimes it doesn't work