configs/freescale_{p1025twr, t1040d4rdb}: headers version
The freescale p1025twr and t1040d4rdb defconfigs use a 4.15 series kernel;
specify BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15 accordingly.
This fixes the following build error:
Incorrect selection of kernel headers: expected 4.16.x, got 4.15.x
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>