ARM: dra7xx: Change DPLL_PER_HS13 divider value

ARM: dra7xx: Change DPLL_PER_HS13 divider value

According to AM572x DM SPRS953A, QSPI bus speed can be 76.8MHz, hence
update QSPI input clock divider value (DPLL_PER_HS13) to provide 76.8MHz
clock, so that driver can use the same.

Signed-off-by: Vignesh R <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Reviewed-by: Mugunthan V N <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>