config: unify RTC_AEC module build process across all platforms

This patch removes the CONFIG_LIBRARY_BUILD_LIB option from the MTPM and
PTL platform configurations to ensure consistent build behavior across
all platforms. The RTC_AEC module was built as an LLEXT module on all
platforms, but the library was only present in the LNL platform during
CI builds due to the enabled CONFIG_LIBRARY_BUILD_LIB option in MTPM and
PTL, which caused discrepancies in the build process.

Changes include:
- Removing CONFIG_LIBRARY_BUILD_LIB from the intel_adsp_ace15_mtpm.conf
  configuration file.
- Removing CONFIG_LIBRARY_BUILD_LIB from the intel_adsp_ace30_ptl.conf
  configuration file.

This change ensures that the RTC_AEC module library is consistently
present across all platforms during CI builds, resolving the issue where
the library was only present in the LNL platform.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>

Author: tmleman

app/boards/intel_adsp_ace15_mtpm.conf

@@ -55,7 +55,6 @@ CONFIG_INTEL_MODULES=y
 CONFIG_LIBRARY_MANAGER=y
 CONFIG_LIBRARY_AUTH_SUPPORT=y
 CONFIG_LIBRARY_BASE_ADDRESS=0xa0688000
-CONFIG_LIBRARY_BUILD_LIB=y
 
 # SOF / logging
 CONFIG_SOF_LOG_LEVEL_INF=y

app/boards/intel_adsp_ace30_ptl.conf

@@ -45,7 +45,6 @@ CONFIG_ZEPHYR_NATIVE_DRIVERS=y
 CONFIG_INTEL_MODULES=y
 CONFIG_LIBRARY_MANAGER=y
 CONFIG_LIBRARY_BASE_ADDRESS=0xa0688000
-CONFIG_LIBRARY_BUILD_LIB=y
 CONFIG_LIBRARY_DEFAULT_MODULAR=n
 
 # SOF / logging