sframe: Add support for SFRAME_F_FDE_FUNC_START_PCREL flag

sframe: Add support for SFRAME_F_FDE_FUNC_START_PCREL flag

The Sframe V2 has a new errata which introduces the
SFRAME_F_FDE_FUNC_START_PCREL flag. This flag indicates the encoding
of the SFrame FDE function start address field like this:

- if set, sfde_func_start_address field contains the offset in bytes
to the start PC of the associated function from the field itself.

- if unset, sfde_func_start_address field contains the offset in bytes
to the start PC of the associated function from the start of the
SFrame section.

Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
Reviewed-by: Sam James <sam@gentoo.org>