kni: fix missing backslash in Makefile
kni: fix missing backslash in Makefile

With GNU Make 3.81 on Ubuntu 14.04, I get:
lib/librte_eal/linuxapp/kni/Makefile:49: *** unterminated call to function `shell': missing `)'.  Stop.

Signed-off-by: Julien Cretin <df52cc2c62e57ad698eea4bcc15941bce8df04c8@trust-in-soft.com>
Acked-by: Thomas Monjalon <ee2fa8b2681c737f775687e475dcbf2028a412f1@6wind.com>

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk