leds: qpnp-flash-v2: Fix the macro calculations

Some of the macros used for calculations are incorrect when
values like 0 are passed. Fix them.

CRs-Fixed: 2165402
Change-Id: I6428704169a83e420236b58b310bdd1acaa3a948
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>