fix messages in fs/minix

Believe it or not, but in fs/minix/*, the oldest filesystem in the kernel,
something still can be fixed:

    printk("new_inode: bit already set");

"\n" is missing!

While at it, I also removed periods from the end of error messages and made
capitalization uniform.  Also s/i-node/inode/, s/printk (/printk(/

Signed-off-by: Denis Vlasenko <vda@ilport.com.ua>
Signed-off-by: Adrian Bunk <bunk@kernel.org>