qcom: spmi-wled: Rename current-boost-limit to boost-current-limit

Rename the device tree property "qcom,current-boost-limit" to
"qcom,boost-current-limit" and associated variables to follow the
same convention. This reflects the hardware documentation.

Change-Id: I74671e90569ee645dd26c8143a4dbcac695b5b80
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>