TF-A AMU: remove AMU enable info print

Following f3ccf036ec the INFO print in amu_enable is causing
a lot of print outs on UART1 in DEBUG mode especially on PSCI test
cases because CPU_ON or SUSPEND operations call:
cm_prepare_el3_exit => enable_extensions_nonsecure => amu_enable.
PSCI SUSPEND is also very frequent in linux boot cases causing test
timeout failures.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I63581f8fa489d44b3b1d10af3b7f6fdf3af44720

lib/extensions/amu/aarch32/amu.c

@@ -44,7 +44,6 @@ bool amu_group1_supported(void)
 void amu_enable(bool el2_unused)
 {
 	if (!amu_supported()) {
-		INFO("AMU is not implemented\n");
 		return;
 	}
 

lib/extensions/amu/aarch64/amu.c

@@ -46,7 +46,6 @@ void amu_enable(bool el2_unused)
 	uint64_t v;
 
 	if (!amu_supported()) {
-		INFO("AMU is not implemented\n");
 		return;
 	}