ddr: Rework errata A008109, A008378, 009942 workaround

Move errata A008109, A008378, 009942 workaround implementation from
compute_fsl_memctl_config_regs() to  fsl_ddr_set_memctl_regs()
and add register write after each workaround implementation.

Signed-off-by: Jaiprakash Singh <Jaiprakash.singh@nxp.com>
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>