mailmap: Update mail address (lukma)

Update my e-mail address from samsung.com to denx.de
Signed-off-by: NLukasz Majewski <lukma@denx.de>

.mailmap

@@ -34,4 +34,5 @@ Wolfgang Denk <wdenk>
 York Sun <yorksun@freescale.com>
 York Sun <york.sun@nxp.com>
 Łukasz Majewski <l.majewski@samsung.com>
+Lukasz Majewski <lukma@denx.de>
 Mirza <Taimoor_Mirza@mentor.com>