opp: Use %pe to print symbolic error name

Replace PTR_ERR() and %ld with %pe and pass the original pointer directly
to dev_dbg(), dev_warn(), dev_err() or pr_err(). The %pe format specifier
prints a symbolic error name (e.g. -ENOMEM) when CONFIG_SYMBOLIC_ERRNAME
is enabled, otherwise it falls back gracefully and prints the raw integer
value. This makes error messages more readable without any functional
change.

Signed-off-by: Sumeet Pawnikar <sumeet4linux@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>