drivers: dma: Remove double parentheses in if statements

This patch fixes following compilation error when compiling using clang

drivers/dma/dma_stm32.c:364:42: error: equality comparison with
extraneous parentheses [-Werror,-Wparentheses-equality]
        if ((config->head_block->source_address == 0)) {
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
drivers/dma/dma_stm32.c:364:42: note: remove extraneous parentheses
around the comparison to silence this warning
        if ((config->head_block->source_address == 0)) {
            ~                                   ^   ~

Signed-off-by: Patryk Duda <pdk@semihalf.com>