remoteproc: elf_loader: Introduce a common elf loader and checker functions

Introduce a common remoteproc elf loader and checker functions that
automatically detects the 64 bit elf file or 32 bit elf file and
loads/checks the sections accordingly.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Fabien Dessenne <fabien.dessenne@st.com>