firmware: qcom: scm: Refactor code to support multiple dload mode

Currently on Qualcomm SoC, download_mode is enabled if
CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT is selected or
passed a boolean value from command line.

Refactor the code such that it supports multiple download
modes and drop CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT config
instead, give interface to set the download mode from
module parameter while being backword compatible at the
same time.

Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
Link: https://lore.kernel.org/r/20240715155655.1811178-1-quic_mojha@quicinc.com


Signed-off-by: Bjorn Andersson <andersson@kernel.org>