core: fix compile error when CFG_TEE_CORE_MALLOC_DEBUG=y
core: fix compile error when CFG_TEE_CORE_MALLOC_DEBUG=y

When CFG_TEE_CORE_MALLOC_DEBUG is enabled, but CFG_TEE_CORE_DEBUG is
not, the compiler complains about unused parameters/functions. Fix them
by adding __maybe_unused qualifiers.

lib/libutils/isoc/bget_malloc.c: In function ‘assert_header’:
lib/libutils/isoc/bget_malloc.c:688:44: error: unused parameter ‘hdr’ [-Werror=unused-parameter]
 static void assert_header(struct mdbg_hdr *hdr)
                                            ^
lib/libutils/isoc/bget_malloc.c: At top level:
lib/libutils/isoc/bget_malloc.c:595:16: error: ‘bget_buf_size’ defined but not used [-Werror=unused-function]
 static bufsize bget_buf_size(void *buf)
                ^
cc1: all warnings being treated as errors

Signed-off-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>
Reviewed-by: Joakim Bech <741f90e2a7f4d9afbad8bd50be20560f4cf38962@linaro.org>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

pascal-brand-st-dev/optee_os,matt2048/optee_os,matt2048/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os