meta-skeleton: fix spaces in assignment

There is now a warning for = without spaces. Fix it also in
meta-skeleton.

(From OE-Core rev: bc2f794b8c95d44522051f63421e2bf38747bd73)

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb

@@ -62,7 +62,7 @@ LINUX_VERSION_EXTENSION:append = "-custom"
 # Modify SRCREV to a different commit hash in a copy of this recipe to
 # build a different release of the Linux kernel.
 # tag: v4.2 64291f7db5bd8150a74ad2036f1037e6a0428df2
-SRCREV_machine="64291f7db5bd8150a74ad2036f1037e6a0428df2"
+SRCREV_machine = "64291f7db5bd8150a74ad2036f1037e6a0428df2"
 
 PV = "${LINUX_VERSION}+git"