cleanup/SPEAr: Define configuration flags more elegantly

In SPEAr, some of the configuration flags eg. CONFIG_SPEAR_EMI, were given value
"1", which isn't required. Define the flags without assigning any value

Signed-off-by: Amit Virdi <amit.virdi@st.com>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>