raid6/algos.c : bug fix : Add the missing definitions to the pq.h file

Adding these pr_info and pr_err definitions so as to allow code to be
compiled successfully for testing in userspace, since the printk has
been replaced by pr_info and pr_err in algos.c

Absence of these definitions result in the compilation errors
such as ' undefined reference to `pr_info' ' ' undefined reference to
`pr_err' '

Cc: NeilBrown <neilb@suse.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>