[CIFS] Rename md5 functions to avoid collision with new rt modules

When rt modules were added they (each) included their own md5
with names which collided with the existing names of cifs's md5 functions.

Renaming cifs's md5 modules so we don't collide with them.

> Stephen Rothwell wrote:
> When CIFS is built-in (=y) and staging/rt28[67]0 =y, there are multiple
> definitions of:
>
> build-r8250.out:(.text+0x1d8ad0): multiple definition of `MD5Init'
> build-r8250.out:(.text+0x1dbb30): multiple definition of `MD5Update'
> build-r8250.out:(.text+0x1db9b0): multiple definition of `MD5Final'
>
> all of which need to have more unique identifiers for their global
> symbols (e.g., rt28_md5_init, cifs_md5_init, foo, blah, bar).
>

CC: Greg K-H <gregkh@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>