compat: fix compat_firmware_class.c compilation on older kernels

compat: fix compat_firmware_class.c compilation on older kernels

CONFIG_COMPAT_FIRMWARE_CLASS is defined explicitly for any kernel >= 2.6.33
but CONFIG_FW_LOADER) || CONFIG_FW_LOADER_MODULE may still be disabled,
and in those cases we should still compile.

Lets clean this up by being explicit about the exported symbols within
compat_firmware_class.c instead of relying on the header file to rename them
for us at compile time. At the same time be consistent and use the
CONFIG_FW_LOADER) || CONFIG_FW_LOADER_MODULE checks on the header
to see which declarations to use.

mcgrof@tux ~/compat (git::master)$ ckmake
Trying kernel                  3.3.0-030300rc2-generic  [OK]
Trying kernel                     3.2.2-030202-generic  [OK]
Trying kernel                    3.1.10-030110-generic  [OK]
Trying kernel                    3.0.18-030018-generic  [OK]
Trying kernel                  2.6.39-02063904-generic  [OK]
Trying kernel                        2.6.38-13-generic  [OK]
Trying kernel                  2.6.38-02063808-generic  [OK]
Trying kernel                  2.6.37-02063706-generic  [OK]
Trying kernel                  2.6.36-02063604-generic  [OK]
Trying kernel                  2.6.35-02063512-generic  [OK]
Trying kernel                  2.6.34-02063410-generic  [OK]
Trying kernel                  2.6.33-02063305-generic  [OK]
Trying kernel                  2.6.32-02063255-generic  [OK]
Trying kernel                        2.6.31-22-generic  [OK]
Trying kernel                  2.6.31-02063113-generic  [OK]
Trying kernel                  2.6.30-02063010-generic  [OK]
Trying kernel                  2.6.29-02062906-generic  [OK]
Trying kernel                  2.6.28-02062810-generic  [OK]
Trying kernel                    2.6.27-020627-generic  [OK]
Trying kernel                    2.6.26-020626-generic  [OK]
Trying kernel                    2.6.25-020625-generic  [OK]
Trying kernel                    2.6.24-020624-generic  [OK]

Cc: stable@orbit-lab.org
Signed-off-by: Luis R. Rodriguez <mcgrof@frijolero.org>