net/dhcp: Consistently use decimal numbers for DHCP/BOOTP options enum

net/dhcp: Consistently use decimal numbers for DHCP/BOOTP options enum

The DHCP Options and BOOTP Vendor Extensions enum values are a mixture of
decimal and hexadecimal numbers. Change this to consistently use decimal
numbers for all since that is how these values are defined by RFC 2132.

Suggested-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>