linux: may fail to boot for binutils 2.29+ even without armv7m

linux: may fail to boot for binutils 2.29+ even without armv7m

Commit f13477b (linux: config.in: add comment for Arm Cortex-M) added a
comment so that the user that the linux kernel may miscompile with
binutils 2.29+, when the target is an armv7m CPU.

However, the real trigger is a compilation in thumb2 mode, which happens
to be the only option for armv7m CPUs.

We can't know whether the kernel will be built in arm or thumb2 mode,
though, because we do not have that information: it is only available in
the Linux' .config file, which we don;t have access to at the time we
run our menuconfig.

So, relax the conditions under which the comment is made, so that it
appears as soon as binutils are >= 2.29 (i.e. not 2.28, which is the
oldest we support) for ARM CPUs.

[Peter: reword comment]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Christophe Priouzeau <christophe.priouzeau@st.com>
Cc: Laurent GONZALEZ <br22@gezedo.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>