arm: cpu: armv7m: add ENTRY/ENDPROC macros

arm: cpu: armv7m: add ENTRY/ENDPROC macros

Since GNU binutils version 2.44, assembly functions must include
the assembler directive .type name, %function. If not a call to
these functions fails with the error message 'Unknown destination
type (ARM/Thumb)' and the error message 'dangerous relocation:
unsupported relocation' at linking.

The macros ENTRY/ENDPROC includes this directive and should be
used for all assembly functions.

Signed-off-by: Johannes Krottmayer <johannes@krotti42.com>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>