Commit b91d935
("Add CFI debug frame information for ASM functions") modifies the
assembly macros 'func' and 'endfunc' to include CFI debug frame
information.

The rockchip platform uses a custom version of the 'func' macro with the
common 'endfunc' macro. The custom macro wasn't updated in
b91d935 resulting in the following
build error:
  plat/rockchip/rk3399/drivers/pmu/plat_pmu_macros.S: Assembler messages:
  plat/rockchip/rk3399/drivers/pmu/plat_pmu_macros.S:155: Error: .cfi_endproc without corresponding .cfi_startproc
  Makefile:532: recipe for target 'build/rk3399/release/bl31/plat_helpers.o' failed
  make: *** [build/rk3399/release/bl31/plat_helpers.o] Error 1

Fixing this by updating the sram_func macro in the rk3399 port.

Fixes: b91d935 ("Add CFI debug frame information for ASM functions")
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>