Remove the function i5100_recmema_dm_buf_id() that is not used anywhere.

This was partially found by using a static code analysis program called
cppcheck.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Link: http://lkml.kernel.org/r/1420999030-21770-1-git-send-email-rickard_strandqvist@spectrumdigital.seSigned-off-by: Borislav Petkov <bp@suse.de>