testsuite: coverage: fix arm64 build with gcov enabled

On ARM64 the build will fail with coverage and GCOV enabled:

  CONFIG_COVERAGE=y
  CONFIG_COVERAGE_GCOV=y
  CONFIG_FORCE_COVERAGE=y

west build -b rpi_5 -p always samples/hello_world -- \
 -DCONFIG_COVERAGE=y -DCONFIG_FORCE_COVERAGE=y

Failure:
 "linker_zephyr_pre0.cmd:181: undefined symbol `__gcov_bss_end' referenced
in expression"

Fix build of ARM64 platforms with coverage and GCOV enabled by adding for
ARM64 the same gcov linker sections as it is done for ARM.

Signed-off-by: Grygorii Strashko <grygorii_strashko@epam.com>

subsys/testsuite/coverage/coverage_ram.ld

@@ -6,7 +6,7 @@
 
 /* Copied from linker.ld */
 
-#ifdef CONFIG_ARM
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
 SECTION_DATA_PROLOGUE(_GCOV_BSS_SECTION_NAME,(NOLOAD),)
 {
 #ifdef CONFIG_USERSPACE