spi: a3700: Remove endianness swapping functions when accessing FIFOs

Fixes the following sparse warnings :
line 504: warning: incorrect type in assignment (different base types)
line 504:    expected unsigned int [unsigned] [usertype] val
line 504:    got restricted __le32 [usertype] <noident>
line 527: warning: cast to restricted __le32

This is solved by removing endian-converson functions, since the
converted values are going through readl/writel anyway, which take care
of the conversion.

Fixes: 6fd6fd68 ("spi: armada-3700: Fix padding when sending not 4-byte aligned data")
Signed-off-by: Maxime Chevallier <maxime.chevallier@smile.fr>
Reviewed-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>