Revert "mfd: syscon: Remove repetition of the regmap_get_val_endian()"

This reverts commit 72a95859.

It broke reboots on big-endian MIPS and MIPS64 malta QEMU instances,
which use the syscon driver.  Little-endian is not effected, which means
likely it's important to handle regmap_get_val_endian() in this function
after all.

Fixes: 72a95859

 ("mfd: syscon: Remove repetition of the regmap_get_val_endian()")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Lee Jones <lee@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>