spi: s3c64xx: rename goto labels to meaningful names

The goto labels of the style of

  err4:
  err3:
  err2:
  err1:

are complex to insert in between new errors without renaming all
the goto statements. Replace the errX naming style to meaningful
names in order to make it easier to insert new goto exit points.

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>