ktest: Let IF keyword take comparisons

Allow ==, !=, <=, >=, <, and > to be used in IF statements
to compare if a section should be processed or not.

For example:

BITS := 32

DEFAULTS IF ${BITS} == 32
MIN_CONFIG = ${CONFIG_DIR}/config-32
ELSE
MIN_CONFIG = ${CONFIG_DIR}/config-64

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>