package/x265: enable parallel build

Parallel builds were disabled in 2018:
https://git.buildroot.net/buildroot/commit/?id=03bfbc5ab26c9aed0c0cfce55341a1d1f05deca3

Build-testing the version bump to 3.5 showed no errors with 32 threads.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/x265/x265.mk

@@ -12,7 +12,6 @@ X265_LICENSE_FILES = COPYING
 X265_CPE_ID_VENDOR = multicorewareinc
 X265_SUBDIR = source
 X265_INSTALL_STAGING = YES
-X265_MAKE = $(MAKE1)
 
 ifeq ($(BR2_i386)$(BR2_x86_64),y)
 X265_DEPENDENCIES += host-nasm