trivial: Style changed files

platsupport: Remove weak subsystem init symbols

Having the clock and mux subsystem initialisation functions be a weak
symbol presents a number of problems. One of these problems is that the
linker may stop looking for other suitable symbols in other external
libraries.

platsupport: Provide default subsystem init impls

clock_sys_init and mux_sys_init functions now have a WEAK symbol
definition. If a platform provides a strong symbol definition, the
linker will override the default.

Fixed warnings found by clang

~/seL4test/libs/libplatsupport/src/arch/arm/clock.c:45:22: warning: comparison of unsigned enum expression >= 0 is always true [-Wtautological-compare]
((void)((clk->id >= 0 && clk->id < NCLOCKS) || (__assert_fail("clk->id >= 0 && clk->id < NCLOCKS", "~/seL4test/libs/libplatsupport/src/arch/arm/clock.c", 45, __func__),0)));
~~~~~~~ ^ ~
~/seL4test/libs/libplatsupport/src/arch/arm/clock.c:70:12: warning: comparison of unsigned enum expression < 0 is always false [-Wtautological-compare]
if (id < 0 || id >= NCLOCKS) {
~~ ^ ~
~/seL4test/libs/libplatsupport/src/arch/arm/clock.c:105:12: warning: comparison of unsigned enum expression < 0 is always false [-Wtautological-compare]
if (id < 0 || id >= NCLOCKS) {
~~ ^ ~
~/seL4test/libs/libplatsupport/src/arch/arm/clock.c:116:12: warning: comparison of unsigned enum expression < 0 is always false [-Wtautological-compare]
if (id < 0 || id >= NCLOCKS) {
~~ ^ ~
4 warnings generated.

fix licenses

Remove trailing whitespace

libplatsupport: Qualify a char * parameter.