ARM: owl: smp: Drop owl_secondary_boot()

Commit 18cfd942 simplified the S500 SMP
code by removing a loop for pen_release in owl_secondary_boot().

Since then it is only calling owl_v7_invalidate_l1() before branching to
secondary_startup().

The owl_v7_invalidate_l1() assembler function is superfluous, too.
Therefore drop owl_secondary_boot() and use secondary_boot() directly.

Fixes: 18cfd942 ("ARM: owl: smp: Drop bogus holding pen")
Cc: David Liu <liuwei@actions-semi.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>