power: qpnp-fg: read SRAM in one burst

Currently, when doing a SRAM dump or a debugfs SRAM read, the fuel gauge
driver does reads in chunks of 4 bytes. This is actually undesirable
because it generates a lot more SPMI writes. It also makes turning on
debug logs for MEMIF reads and SPMI reads/writes impossible, as doing
large dumps of the SRAM will crash the system due to excessive logging.

Fix this by doing the SRAM reads in one burst transaction instead of
doing it in pieces.

CRs-Fixed: 738872
Change-Id: I751755ace699f672befdd1e49213b1c08fe078cf
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>