isofs: add KERN_CONT to printing of ER records

The ER records are printed without explicit log level presuming line
continuation until "\n".  After the commit 4bcc595c

 (printk:
reinstate KERN_CONT for printing continuation lines), the ER records are
printed a character per line.

Adding KERN_CONT to appropriate printk statements restores the printout
behavior.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>