Added missing checks to avoid null pointer dereference.

The patch fixes below issue reported by klocwork tool:
. Pointer 'strsep( &val, ":" )' returned from call to function 'strsep'
  at line 1608 may be NULL and will be dereferenced at line 1608. Also
  there are 2 similar errors on lines 1620, 1632 in otx2_cptpf_ucode.c.
Signed-off-by: Shijith Thotton <sthotton@marvell.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>