ARM: s3c: fix fiq for clang IAS

ARM: s3c: fix fiq for clang IAS

Building with the clang integrated assembler produces a couple of
errors for the s3c24xx fiq support:

  arch/arm/mach-s3c/irq-s3c24xx-fiq.S:52:2: error: instruction 'subne' can not set flags, but 's' suffix specified
    subnes pc, lr, #4 @@ return, still have work to do

  arch/arm/mach-s3c/irq-s3c24xx-fiq.S:64:1: error: invalid symbol redefinition
    s3c24xx_spi_fiq_txrx:

There are apparently two problems: one with extraneous or duplicate
labels, and one with old-style opcode mnemonics. Stefan Agner has
previously fixed other problems like this, but missed this particular
file.

Fixes: bec0806cfec6 ("spi_s3c24xx: add FIQ pseudo-DMA support")
Cc: Stefan Agner <stefan@agner.ch>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20210204162416.3030114-1-arnd@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>