Commit 06ad970b53 ("powerpc: mpc85xx: Implemente workaround for CPU
erratum A-007907") clears L1CSR2 for the boot core, but other cores
don't run through the workaround. Add similar code for secondary
cores to clear DCSTASHID field in L1CSR2 register.
Signed-off-by: York Sun <york.sun@nxp.com>