ACPI: fix whitespace in pr_fmt() to align log entries

See this dmesg extract before the patch:

[    0.679466] ACPI: Dynamic OEM Table Load:
[    0.679470] ACPI: SSDT 0xFFFF910F6B497E00 00018A (v02 PmRef  ApCst    00003000 INTL 20160422)
[    0.679579] ACPI: Executed 1 blocks of module-level executable AML code
[    0.681477] ACPI : EC: EC started
[    0.681478] ACPI : EC: interrupt blocked
[    0.684798] ACPI: Interpreter enabled
[    0.684835] ACPI: (supports S0 S3 S4 S5)

Signed-off-by: Vincent Legoll <vincent.legoll@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>