package/gdb: make gdb 9.2 the default version

package/gdb: make gdb 9.2 the default version

Now that we have added gdb 10.1, let's switch to using gdb 9.2 as the
default version.

Noe that there previously was a discrepancy between the default when a
host gdb was enabled, and when it was not: in the ofrmer case, the
default was 8.3.x, while for the latter it was 8.2.x. Now both are
aligned to 9.2.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
[yann.morin.1998@free.fr: add blurb about previous version discrepancy]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>