defconfigs: fix typo in selftests defconfig filenames

All selftests defconfig files were incorrectly named with "seltests-*"
instead of "selftests-*", missing the 'f' from "self". This typo is
inconsistent with the workflow name (workflows/selftests/), make
targets (selftests-*), Kconfig symbols (CONFIG_SELFTESTS_SECTION_*),
and Linux kernel convention (tools/testing/selftests/).

Rename all eight affected defconfig files and update the three symlinks
(linux-firmware-kpd, linux-mm-kpd, linux-modules-kpd) to point to the
corrected filenames.

Generated-by: Claude AI
Signed-off-by: Daniel Gomez <[email protected]>

Author: dkruces

PROMPTS.md

@@ -57,7 +57,7 @@ kdevops in-kernel and then in userspace. The in-kernel testing done requires
 using a loadable kernel module for each.
 
 We have support for bundling these two tests under the
-defconfigs/seltests-radix-tree defconfig and we use the
+defconfigs/selftests-radix-tree defconfig and we use the
 SELFTESTS_TEST_BUNDLE_RADIX_TREE to help us bundle all radix-tree related tests.
 We want to extend this with a new userspace only test. Its the vma tests on the
 Linux kernel. So it won't have a corresponding Linux kernel module load,

defconfigs/linux-firmware-kpd

@@ -1 +1 @@
-seltests-firmware
+selftests-firmware

defconfigs/linux-mm-kpd

@@ -1 +1 @@
-seltests-radix-tree
+selftests-radix-tree

defconfigs/linux-modules-kpd

@@ -1 +1 @@
-seltests-modules
+selftests-modules