Removed miosix kernel submodule

.gitmodules

@@ -1,4 +0,0 @@
-[submodule "lib/miosix-kernel"]
-	path = lib/miosix-kernel
-	url = https://github.com/OpenRTX/miosix-kernel.git
-        branch = release

cross_arm.txt

@@ -55,7 +55,6 @@ c_link_args = [
                '-Wl,-Map,main.map',
                '-Wl,--warn-common',
                '-nostdlib',
-               '-lmiosix',
                '-lstdc++',
                '-lc',
                '-lm',

lib/miosix-kernel

@@ -1 +0,0 @@
-Subproject commit fef1263a5df00d0f5d979e173c635d83be9388d1