Fix: Resolve multiple definition linker error

Added the `inline` keyword to `uefi::cper::convertToBcd` and
`uefi::cper::createCperTimestamp` functions in `cper_encoder.hpp`.
This resolves a linker error caused by multiple definitions of these
functions when `cper_encoder.hpp` was included in multiple source files.

Tested: Fixes build failures in https://gbmc-internal-review.git.corp.google.com/c/deepsea-power-cap/+/244408
Google-Bug-Id: 424199978
Change-Id: I8fd86b8204b4406e6492b61e96c5f8b293d13888
Signed-off-by: Gaurav Gandhi <gauravgandhi@google.com>

include/cper_encoder.hpp

diff --git a/include/cper_encoder.hpp b/include/cper_encoder.hpp
index 4258cf1..f80f781 100644
--- a/include/cper_encoder.hpp
+++ b/include/cper_encoder.hpp
@@ -23,7 +23,7 @@
  *
  * @returns a byte with the BCD val.
  */
-uint8_t convertToBcd(uint8_t val)
+inline uint8_t convertToBcd(uint8_t val)
 {
     return (0x10 * (val / 10)) + (val % 10);
 }
@@ -39,7 +39,7 @@
  *
  * @param[out] A uefi cper timestamp as uint64_t.
  */
-uint64_t createCperTimestamp(
+inline uint64_t createCperTimestamp(
     const std::chrono::time_point<std::chrono::system_clock> timeOfCollection,
     const bool isPrecise = true)
 {