spi: geni-qcom: Improve target mode allocation by using proper allocation functions

spi: geni-qcom: Improve target mode allocation by using proper allocation functions

The current implementation always allocates a host controller and sets the
target flag later when the "spi-slave" device tree property is present.
This approach is suboptimal as it doesn't utilize the dedicated allocation
functions designed for target mode.

Use devm_spi_alloc_target() when "spi-slave" device tree property is
present, otherwise use devm_spi_alloc_host(). This replaces the previous
approach of always allocating a host controller and setting target flag
later.

Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://patch.msgid.link/20260204162854.1206323-2-praveen.talari@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>