init/main.c: don't use pr_debug()

init/main.c: don't use pr_debug()

Pertially revert ea676e846a8171b8 ("init/main.c: convert to pr_foo()").

Unbeknownst to me, pr_debug() is different from the other pr_foo() levels:
pr_debug() is a no-op when DEBUG is not defined.

Happily, init/main.c does have a #define DEBUG so we didn't break
initcall_debug.  But the functioning of initcall_debug should not be
dependent upon the presence of that #define DEBUG.

Reported-by: Russell King <rmk@arm.linux.org.uk>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>